In a characteristically cryptic but illuminating speech to mark the start of the Christian Holy Week, Pope Benedict XVI made it clear today that he would not intimidated by his critics over the ongoing sexual abuse scandal enveloping his church.

Speaking at a Palm Sunday service in Rome in front of tens of thousands of worshippers, the 82-year-old pontiff made no official mention of global clerical sex abuse scandals that have thrown the church into its worst crisis in recent decades.

But he did launch a clear broadside against those who have called on him to do more to explain his previous role as the Vatican’s head investigator of child abuse claims.

In his Palm Sunday address the Pope reminded worshippers that belief in Jesus Christ helped lead Christians “towards the courage of not allowing oneself to be intimidated by the petty gossip of dominant opinion.” He also spoke of how man can sometimes "fall to the lowest, vulgar levels" and "sink into the swamp of sin and dishonesty".

The remarks are widely regarded as a reference to the growing furore over his leadership of the Congregation for the Doctrine of the Faith which the German-born pontiff was in charge of for more than twenty years before becoming Pope in 2005. The Congregation is responsible for maintaining the church’s moral and doctrinal purity. One of its primary remits includes investigating any clerical abuse allegations that are put before it.

But the growing sexual abuse scandals emerging out of mainland Europe, Ireland and North America have put the Vatican, and the Pope himself, firmly on the back foot as critics and abuse victims have called on Benedict to open up the Congregation’s files to see how the department handled abuse allegations. Some have even gone as far as calling for the Pope to resign.

The Vatican has responded by going on the offensive, describing the personal criticism of its leader as an "ignoble attempt" to smear both the Pope and his top advisers "at any cost".

Today’s remarks were widely perceived to be a continuation of that tactic and a clear indication that the Pope would not be drawn into commenting publicly on sexual abuse at the whim of the Vatican’s critics or abuse victims.

But with new sex abuse scandals emerging around the world each week, church officials are struggling to avoid the issue dominating the international agenda. This afternoon Swiss president Doris Leuthard called for a central register for paedophile priests to ensure they never work with children again. "Whether perpetrators come from the civil or clerical world makes no difference. Both are subject to Swiss criminal law, with no ifs or buts," Leuthard said. Swiss police are currently investigating a number of abuse complaints against clergy which emerged shortly after similar investigation in the Netherlands and Germany.

In Britain, meanwhile, a small group of approximately 50 protestors gathered outside Westminster Cathedral as the leader of Britain’s Catholics, Archbishop Vincent Nichols, conducted his Palm Sunday mass.

The protest was the first major outing for the “Protest the Pope” movement, a coalition of secularists and human rights campaigners who are opposed to Benedict’s upcoming state visit to Britain later this year.

They have vowed to follow the Pope during his visit to Scotland and England this September, including keeping a constant vigil outside Holyroodhouse in Edinburgh when Benedict meets the Queen there. They also plan to hold demonstrations outside the residence of the Vatican’s papal nuncio (ambassador) in Wimbledon where the Pope will stay during his time in London.

The coalition is opposed to the Pope’s visit being partially funded by the UK tax payer. They are critical of the Roman Catholic leader on a number of reasons, particularly his hardline stance on abortion and condoms. But the ongoing sex abuse scandal has given the group added impetus to try and expand their protest movement before the Pope even arrives in Britain.

Human rights campaigner Peter Tatchell, one of Protest the Pope founders, said yesterday that they were currently investigating whether it would be possible to launch a criminal investigation of the Pope’s handling of historical abuse inquiries. Similar tactics were used by pro-Palestinian groups shortly after Israel’s offensive last year in Gaza to stop a number of key Israeli political and military figures travelling to Britain.

“The evidence clearly shows that the Pope was an accomplice to the cover up of a series of sex crimes,” Mr Tatchell said. “We intend to investigate the possibility of the Pope being prosecuted as an accomplice to the cover up of sex crimes against young people.”

The Pope’s supporters, meanwhile, have rallied to defend their leader arguing that as head of the Congregation he was responsible for making sure that abuse allegations were adequately investigated.

Speaking on the BBC’s Andrew Marr show, Archbishop Nichols defended his boss in Rome. "[The Pope] pushed forward for example a fast-track to defrock priests who have committed abuse,” he said. “He changed the statute of limitations in Church law. He changed the law so that sexual offences committed with anyone under the age of 18 would be a crime in Church law."

Asked whether he thought the Pope would ever resign (only two pontiffs have ever resigned in the past 2,000 years), Archbishop Nichols remarked: “The pope won't resign. Frankly there's no strong reason for him to do so.”