In February, this man was led to the death chamber in a Philippines prison. His crime: the repeated rape of his 10-year-old stepdaughter. A Briton, Albert Wilson, is among more than 400 other inhabitants of Manila's death row who have also been convicted of child rape since the law was tightened in 1994. But evidence suggests that many may not be guilty, while their `victims' have much to gain from convictions. Philip Sweeney investigates

Muntinlupa Penitentiary presents an odd mixture of the serene and the sinister after the fumes and din of a 90- minute ride in a Jeep from downtown Manila. On a low hill, the prison's main complex is a rambling, crenellated Thirties fortress set amid terraced grassland. Its gates are surrounded by "Jeepneys" and motor tricycles bringing visitors and also an encampment of food stalls and cigarette stands. Go around the side wall and there's a new terracotta-coloured glass-roofed building with trim hedges that looks rather like a smart suburban garden centre, apart from the shiny gold lettering that declares, "Lethal Injection Chamber".

This is where Leo Echegaray, the first Filipino to be executed for 23 years, took his last breaths early in February. He began snoring as the first shot of thiopental sodium put him under, ready for the potassium chloride that would stop his heart. Beyond a police cordon, a circus of pro- and anti-death penalty activists sang and chanted.

Echegaray was convicted of child rape, a capital offence since 1994 in the Philippines. As public awareness of child sexual abuse, previously a common but unreported phenomenon, has raised in recent years, largely by foreign charities and pressure groups, denunciations for the offence have rocketed. Today, more than half of the 900 Filipinos on death row have been convicted of child rape.

Though conviction in the Philippines, as elsewhere, does not necessarily indicate guilt. According to Roan Libarios, a congressman trying to set up an inquiry into the fairness of Echegaray's trial, "half the convicts in the Muntinlupa Penitentiary are not guilty as charged".

The Echegaray case revealed a dangerous new development: big rewards for rape victims. "Baby" Echegaray, the executed man's victim and stepdaughter, received money, plots of land and film offers as a result of her TV appearances with former actor Joseph Estrada, the John Wayne of the Philippines, now the country's gung-ho pro-death president. Indeed, all sexual assault sentences include compensation by the convicted to the victim, 50,000 to 100,000 pesos (pounds 1,000 to pounds 2,000), a major windfall for a poor family, of which there are many in this country.

"Fake Rape Victims!" shouts a headline from a paper I buy through the window of the Jeep, over a story about a senate proposal to increase the penalty for false accusations resulting in death sentences to 30 years' jail.

The British Foreign Office travel advice for visitors to the Philippines now notes, among malaria risks and typhoon warnings, the danger of the death penalty for paedophile activity, and the occurrence of "cases of entrapment". And, in an attempt to improve the quality of prosecutions, the British Government is sending UK specialists to train the Philippines police following international discussions on the prosecution of sex tourists in their countries of origin.

I'm at Muntinlupa to visit several inmates, discreetly, since this is a particularly bad moment to request press interviews in the prison. A gang battle the previous week has left one prisoner dead, stabbed more than 100 times with the short scalpel blades the inmates keep hidden on strings immersed in the latrines. Now there is a jumpy truce.

Worse, the prison superintendent, a jovial man who on my last visit had entertained me with cups of coffee and an inspection of the contents of one of his desk drawers - a display of hand-grenades confiscated from prisoners - has just been sacked following press disclosures about the conditions of incarceration of one of my potential interviewees, a man conveniently qualified to speak on behalf both of sex criminals and of the Philippines legislature.

Romeo Jalosjos' presence in Muntinlupa demonstrates the seriousness of the Filipino crackdown on paedophiles. Jalosjos, a television presenter, resort owner and congressman, was sentenced to life imprisonment for the rape (in the Philippines, rape includes consensual sex with minors) of a 12-year-old girl.

Consigned to Muntinlupa, Jalosjos continued to exercise his role as congressman. He also made his prison life bearable, which with money and influence is apparently straightforward. Jalosjos rapidly took over an entire dormitory, equipped it with TV, shower, heater and fan, employed inmates as servants, opened a hamburger stand and a tennis club inside the prison grounds, and arranged himself a succession of excursions, for hospital treatments, business meetings and, some papers hinted, meetings of a more carnal type. Unfortunately, I am denied the chance to ask the congressman his views on whether or not the death penalty is appropriate for crimes such as his. For now, Jalosjos is locked in solitary in the grubby white barn-like death-row building, while embarrassed public officials make excuses for his recent lifestyle. I discover all this from another unusual inmate of Muntinlupa's maximum security wing, Albert "Suny" Wilson, a former taxi driver and port worker from Dover, Kent.

Wilson is the first and, for now, the only Briton on death row convicted of the rape of a minor. According to Wilson, the charge stemmed from an attempt at extortion by the alleged victim's father. I talk to Wilson through the bars of the exercise terrace surrounding the death-row block. Wilson, in a singlet and shorts, seems tired, cynical and defiant. How did he get here? "I made the mistake of causing a Filipino to lose face, and to become my enemy. I set up home with this guy's wife. I must have looked as if I had money. I was convicted in spite of the evidence of the girl's mother, all the other relatives and in spite of medical evidence."

Wilson is lucky in having an energetic defender, a Canadian magazine publisher named Wally Moran who has devoted months to a campaign to declare a mistrial, arranging for independent legal and medical assessments of the evidence, enlisting the support of London solicitor Steven Jakobi's organisation, Fair Trials Abroad.

"Judge the trial by the International Convention on Civil and Political Rights of 1966, which the Philippines signed," says Jakobi. "If an ordinary person can see conflicts in evidence, especially medical evidence, then you can't possibly convict beyond reasonable doubt."

From the ample documentation available, these are the salient points of the case: in 1993 Wilson set up home with the mother of Nika, the child, then 12, he is alleged to have raped. Nika's allegations were put forward by the father, who then proposed dropping the charges in return for money. The principal witness for the prosecution was Nika herself, whose testimony was riddled with contradictions and inconsistencies, while the medical evidence failed to show satisfactorily that any rape had taken place. The odd niggle of doubt suggests itself, perhaps.

Wilson awaits his Supreme Court appeal in Muntinlupa, whiling away his days with law books, existing on the daily 38 peso (50p) ration of boiled rice and gristly meat, co-existing warily with the gangs who demand shares of cash and gifts, and see foreign prisoners as likely recipients of both.

Wilson's cell-mates paid the guards to have him put with them.

His cause has attracted a measure of interest in Manila. Not, it seems, among the British expatriate community: an appeal in the Foreign Post for donations to a defence fund attracted just two replies. Individuals and institutions involved in the campaign against child sexual abuse have responded, however.

The Manila bureau of Ecpat, the international anti-child-prostitution group, has commented that the threat of the death penalty makes the pursuit of cases more difficult. And the most outspoken champion of Wilson is an elderly Australian named Earl Wilkinson, a self-proclaimed paedophile hunter.

Wilkinson lives in a 24th-floor apartment in the wealthy financial district of Makati, next door, coincidentally, to the block where Romeo Jalosjos enjoyed the visits of his 12-year-old prostitute. Having made a fortune on the Sydney stock market, Wilkinson retired to devote himself to big game hunting, freelance social activism and the writing of reams of idiosyncratic contributions to the letters pages of the Filipino press. In the early Nineties he took up the paedophile issue, and, often working with the Preda Foundation, another high-profile private prosecutor of paedophiles, began to investigate suspicious men, offer rewards for disappeared suspects, pay maintenance and transport costs to enable victims and witnesses to go through with court actions, and lobby and pursue politicians and the police authorities.

In his living room, along with the photos of himself with slain buffalo and hooked swordfish, are stacks of documents and mementos of his paedophile campaigns: the unmasking of the renegade priest "Father Kiss", a frequenter of the notorious rent-boy town of Pagsanjan, the jailing of Victor Fitzgerald, the first foreign paedophile to be convicted in 1993 ("it was an ambition, we had to get the first one behind bars").

Wilkinson believes that the paedophile prosecution frenzy has still to peak. And, with the added threat of the death penalty, of which he disapproves, he's reconsidering his vigilante work. "There's too big a temptation to blackmail now. Baby Echegaray's money and film contract are infamous. Wilson was framed; he's an innocent man. I'm going over to the defence for a while."

So Wilkinson, with a crucifix hanging around his neck to make him look like a prison chaplain, visits Suny Wilson in Muntinlupa, works on his defence and helps his family.

Not all injustice in Muntinlupa involves the drama of a death sentence. Filipino courts seem to be extraordinarily harsh in general: 16 years' jail for minor embezzlement; 18 for possession of a firearm. I have two more British convicts to visit, who have become friends and spend their afternoons talking in the grounds. The first, John Pidden, is a recent detainee, a building worker from the Midlands sentenced to 14 years for lascivious conduct.

Bemused and uncomplaining, Pidden's voice trembles slightly under the unexpected burden of telling so much correctly in such a short time. Broke, and waiting for a new job contract in Hong Kong, he was sleeping rough in Luneta Park in central Manila when he got talking to an attractive, young woman and they arranged to meet in the park later on.

When she returned, to his slight annoyance, she had her child with her. The afternoon ended outside the grand old Manila Hotel with the woman, and a taxi driver she called to her aid, accusing him of touching the child's leg. Policemen hinted that the matter would be dropped in return for a little drink money and seemed disbelieving when he told them he had none.

Pidden was convicted on the woman's statement alone; neither she nor the child turned up at his trial. And, since he has been in prison, Pidden has seen nothing of the public lawyer who is supposed to be preparing his appeal.

Michael Clarke, Pidden's friend, has his own legal problems. Clarke is a one-time Eastbourne used car dealer in his 50s, his vest revealing profuse arm tattoos. Clarke is three years into a 16-year sentence for procuring child prostitutes, against which he's been trying to appeal. He currently has a bewildering new benefactor, a former nightclub singer called Tony, now a clerk of court, who claims influential family relationships and has arranged, he says, for the legal research staff of the Supreme Court in Manila to prepare an appellant brief in Clarke's case for the Appeal Court.

As we drive south to the prison in Tony's Jeep, my mind boggles more with each new piece of information Tony shouts to me over the roar of the traffic. "The researchers have found 10 technical errors in Clarke's case - only one is needed for a mistrial. They're doing this for much less than a normal lawyer.

"I was asked to help Clarke by the prison chaplain; actually I was in Muntinlupa myself on a drugs charge. See that building - the owner wanted me to open a nightclub in it but I refused." Sitting in a visiting room with Tony, Clarke struggles to fathom his convoluted news. "Is he giving me the runaround? Where exactly is my case now?"

The Clarke case makes interesting reading. And lengthy: Clarke himself has produced dozens of pages of frantic protest from prison, and a loose support group, which counts among its members a German restaurant owner and the Philippine consul in Dublin, has collated police reports, court transcripts and other documents.

Clarke discovered the Philippines and its cheap and ready sex in 1996 and decided to set up as a tour operator. He placed an advertisement under the name Paradise Express in Exchange & Mart and produced a crude brochure, describing an "adult Disneyland" of beautiful, health-checked "starlets" offering an "overnight journey to heaven" for "around pounds 12". Clarke might have prospered, and graduated to genuine pimping, but his grubby little enterprise was stifled at birth.

His nemesis took the form of a coalition of paedophile vigilantes including Earl Wilkinson, the Preda Foundation, led by its crusading priest-investigator Father Shay Cullen, the UK charity Christian Aid and an ITN News team. The Exchange & Mart ad resulted in three bookings: two were from an ITN reporter and a Christian Aid researcher, posing as sex tourists. By the time the third man turned up, Clarke was nowhere to be found, because his first clients had filmed Clarke with a concealed camera and had had him arrested for agreeing that underage prostitutes could be procured. They had then gone home.

Nobody suggested that Clarke actually did procure any girls, young or old, or that Clarke himself initiated the offers. The Filipino police agent who investigated the case found no grounds to prosecute, and Clarke was on the point of being released when Earl Wilkinson, after learning that the quarry was about to escape, called a senator who blocked Clarke's release, while the Preda Foundation's Father Cullen initiated a new set of charges.

North of Manila, the towns of Angeles and Olongapo, where the Preda Foundation has its headquarters, constitute the new red-light zones of the Philippines, since former police general Lim was elected mayor and closed down the sex bars of central Manila. Here, the old vice districts catering until 1991 to the great US military bases (air force at Clark Field, Angeles, and navy at Subic Bay, Olongapo) continue their trade, servicing a motley clientele of middle-aged foreign men.

This was the area where Clarke tried to set up shop: former acquaintances here describe him as an idiot and a fall guy. No one would need a Michael Clarke in Angeles. Girls of 15, 14, even 13, can easily be bought for a "bar fine" of pounds 15. Younger girls, and boys too, are available but the mama-sans - the older women in charge - are wary: the penalties are now severe, and surveillance clandestine and unpredictable. This is due to no one more than Father Shay Cullen.

The Preda Foundation occupies a large house on a wooded hillside with a panoramic view of Subic Bay, the old US naval base far over to the left, small pleasure beaches and villages stretching away to the right. Father Cullen's hectic travel schedule, which includes campaigning, fund-raising, investigating, issuing an unstoppable flow of writs, denunciations, letters and e-mails, makes him difficult to pin down.

Latterly he's been talking to the American authorities about the practicalities of prosecuting offenders back in the US. I caught him between filming with a German TV crew and a Spanish one. Born in Dublin, Cullen arrived in Olongapo as a young missionary, with a strong leaning towards social reform and liberation theology.

He set up Preda in 1974, first as a street-children's drug rehabilitation centre, and moved into tackling child abuse as his charges began to recount grim stories of exploitation: these were the days of Olongapo's notorious "BJ [for blow job] Alley", where impoverished parents sold their kids to US sailors for fellatio.

"Olongapo was Sodom and Gomorrah in those days," says Cullen, standing on the terrace above the sparkling bay. "Just down there was where Fitzgerald's yacht was anchored; our first foreign conviction. I watched through binoculars and saw he had children come aboard."

According to Cullen, Filipino police and courts are easily paid off by sex criminals, so he has become adept at legal manoeuvring to fight back. Preda's cases often amount in effect to private prosecutions with Preda, and not with the State, as complainant, with motions to dismiss judges who fail to convict, and alternative charges filed when the original ones are dismissed, and appeals over the heads of local police and judiciary to ministers.

"Cullen's like a bloodhound," Earl Wilkinson tells me, "and he's got powerful contacts." "He gets his way," says the editor of the local newspaper, "because people are cowed by his authority as an expert, a priest and a European, and because he creates great publicity ... "

Critics of Father Cullen claim that in his zeal to prosecute he cuts corners and a number of court actions are reopening old cases. The girls who gave evidence in the Fitzgerald case have retracted, saying Cullen promised them money to testify falsely. "I merely told them about the 50,000 pesos damages that they would get if he was convicted," the priest comments.

A Swiss national has won damages against a German television company which, allegedly, as part of a Preda-linked documentary, had a 19-year- old girl claim she was 14 for the camera.

That isn't the worst of it. Recently, in a grotesquely complicated series of events revolving around a young girl taken into Preda for investigation, charges of rape have been filed against Cullen himself, charges he dismisses as malicious harassment by a "paedophile support ring". "In the Philippines, you can just tell anything to the press and it'll become public fact," he tells me, without any apparent irony: Cullen's own discourse has a distinct tendency to condemn opponents by association and exaggeration. Was he ever tempted to bend the rules in good cause, if things were so corrupt? I ask. "No, no, no," says Cullen, "that would be stupid, like Bill Clinton, losing our reputation for one slip ... if we're put out of business, there'd be no one helping those kids. "

At the end of my visit, through the morass of accusation and lurid counter- accusation, my mind kept returning to the case of mild-mannered John Pidden. Did he touch the child in the park? I rang his daughter in Northamptonshire for him and she asked resignedly, "Will he really be there for 14 years? I haven't seen him for six years anyway."

I called by the Luneta Park police station but found out nothing. The Manila Hotel disclaimed any knowledge of the events. In the end, that hoariest of journalistic sources, a taxi driver came up trumps. About to leave for the airport, I went to the Manila Hotel taxi pool and asked the drivers sitting under a tree if anyone remembered the English sex-assault case. A middle-aged driver was summoned. "Yes, I was there when it happened." We loaded my case and set off for the airport.

"I'm pleased you asked," he said, "because we were worried after the Englishman went to prison. We even tried to tell some journalists in the hotel, but no one was interested. We realised later that the woman was a swindler."

Apparently, the taxi driver who was enlisted to give evidence against Pidden had taken up with the woman, who said she was expecting a large sum of money. "He didn't work for a month, just accompanied the woman around. She said she would buy him his own taxi - then she disappeared. By then he owed the owner of his taxi 20,000 pesos rent ... he still does, he's lost his job. I'm sure he will say this officially."

Back in the UK, I related the Pidden story to Steven Jakobi, who sighed wearily and reminded me of the Sixties English criminal jargon "badger game", denoting the practice whereby wealthy mugs were lured into hotel rooms by young women whose "husbands" then burst in angrily demanding money to keep quiet. What are the chances of bringing prosecutions of UK paedophiles before British juries, using evidence from the Philippines? I asked Jakobi, who is a consultant for the EU on cross-national trial procedures. "In Europe, preparing for the process will take another five to 10 years," he replied. "In a place like the Philippines, a generation or two, I'd say. So a cat in hell's chance, basically"

Captions: Opposite page: Leo Echegaray is led to the death chamber at Muntinlupa Penitentiary.

Above: protesters picket a courthouse where an 11-year-old rape victim was confronting her accused, the congressman and TV presenter Romeo Jalosjos. He has since been sentenced to life imprisonment. Left: child sexual abuse has long been rife but unreported in the Philippines. The tightening of the law was intended to encourage reporting of such cases and to curb sex tourism

Above: Father Shay Cullen, a high- profile paedophile prosecutor, with children at the Preda Foundation, set up to investigate child sex cases. Below: the Foundation occupies a large house on a hillside near the heart of the country's main red-light district

Top: Michael Clarke being secretly filmed by an ITN researcher. Above, centre: solicitor Steven Jakobi of Fair Trials Abroad. Above: paedophile hunter Earl Wilkinson. Below: one of the Manila clubs where foreigners will make their first contact with Filipino girls

Leo Echegaray's wife, Zenaida Javier, prays in front of the gates of the death chamber at Muntinlupa Penitentiary, just two days before her husband was executed after being convicted of child rape