More than 5,000 underage girls are working as prostitutes in Britain, and the number caught soliciting has doubled since 1990, according to a three-month investigation.
Girls aged under 16 were found not only in London but in red-light districts of cities such as Cardiff, Southampton, Manchester, Doncaster and Leeds, and in one case a 12-year-old was caught soliciting.
Recently the focus has been on so-called "sex tourists" who travel abroad but, according to Rob Kiener, who carried out the study for Reader's Digest, there is a growing number of juveniles who sell themselves at home.
Mr Kiener said children in care and runaways are the most vulnerable. But "it's not just some lower class or underclass. There was a girl in Doncaster, 14, living at home, who met her pimp in a bar she had gone to with her brother. Her mum was a hospital physiotherapist."
Although social workers may suspect a girl in care is prostituting herself, by law they cannot physically restrain her. And if the police pick her up they must take her back to social services. Often, unless a girl is in a secure unit, she can be back on the street within hours.
A spokeswoman for the Children's Society, which will launch a national campaign on child prostitution next month, said: "Locking children up isn't an adequate response to the problem of prostitution. But they need to be protected and secure accommodation is an option."
Young girls are frequently lured in through what they see as affection or love. Often starved of attention in their life, they are showered with gifts, clothes and drugs until their "boyfriend/pimp" demands a return on his investment.
When 14-year-old Cassie's pimp believed she was withholding money, he burned her breasts and nipples with a lighted cigarette, then he and three friends gang-raped her "to teach her a lesson". And in Cardiff, three pimps armed with knives, metal bars and a samurai sword forced four teenage girls, the youngest 14, to work as prostitutes. Each night the girls were strip-searched for their earnings, which amounted to more than pounds 1,000 a week.
Even after physical abuse many girls do not leave. "It's like a battered wife who can't leave her husband," said Mr Kiener. "They say things like 'he only beats me because he loves me'."
"Jane" [not her real name], a project worker doing prostitute outreach in West Yorkshire, agreed. "It's a case of 'better the devil you know'. If they leave they lose their friends, where they live and their income," she said. It angers her that it is the girls rather than the pimps or punters who tend to end up with a criminal record.
One solution has been found in Nottingham, after the anti-vice squad found they had arrested twice as many juveniles for soliciting in 1992 as in the previous year. Closer liaison with local authority and social services has meant that, since 1992, nearly 100 pimps have been convicted.
One success was the case of Oswald "Lucky" Golding, who had been suspected for some time. Social workers tipped the police off that a man fitting his description was hanging round a home where two girls, aged 13 and 15, were regularly absconding. The police kept Golding under surveillance, and he was convicted, receiving a two-year jail sentence.
"We took an extremely close look at the girls involved and found many of them were in care." said Inspector Dave Dawson, of Nottingham police. "Many were being forced or intimidated by individual adults to come on the streets. So we targeted the areas where the liaison was formed."
Last year, Doncaster police were told that a 12-year-old was soliciting. They found her several nights later offering herself for pounds 20. After local media coverage, the town's older prostitutes reported an influx of kerb- crawlers asking "if they could get them a 12-year-old girl".