Police chiefs played down fears yesterday that the national launch of the "Sarah's law" sex offender early warning system would drive paedophiles underground and encourage vigilante attacks.
Parents and guardians are to be given the formal right to ask police to look into the background of people with unsupervised access to their children.
The scheme, which follows the murder of eight-year-old Sarah Payne by the convicted sex offender Roy Whiting in 2000, is getting the go-ahead after a year-long trial in four areas.
Theresa May, the Home Secretary, yesterday announced that it would be rolled out across England and Wales. It falls far short of demands from campaigners for the names of all sex offenders in an area to be published.
But charities, criminologists and civil liberties groups have warned that even this diluted version could backfire by fuelling malicious gossip and encouraging paedophiles to change identity and break off contact with the police.
Diana Sutton, the spokeswoman for the NSPCC, said: "The Government needs to tread cautiously in rolling out the scheme to more police forces.
"We remain concerned about the risk of vigilante action and sex offenders going underground. All new local schemes need close management and proper resourcing to avoid this."
Parents concerned about a new partner, or anyone else with regular contact with their child, will be able to request a police check into their background. If the person is found to be a convicted sex offender, the parent who raised the alarm will be warned and given advice on safeguarding their children, along with a warning not to tell anyone else.
The Association of Chief Police Officers (Acpo) welcomed the national roll-out and said it was "realistic" to think people would keep information to themselves.
Sir Hugh Orde, Acpo's president, said: "People say people will go underground – frankly, people go underground anyway. With all the other parts of the police service working also in this area, I do think we have got a real hope of keeping people safer and keeping young people safer, which is very important."
Video: Sarah's law set for national roll-out
The disclosure scheme ran on a trial basis in Cambridgeshire, Cleveland, Hampshire and Warwickshire. Academic research on its application in those areas found no evidence of known paedophiles disappearing, but there were doubts whether it added much to the work already done to monitor offenders after their release.
There was also evidence of fathers registering concerns about their former partner's new boyfriend, possibly as a tactic to undermine a new relationship.
The Home Office said yesterday that there had been almost 600 inquiries to the four forces involved in the pilots, leading to 315 applications for information and 21 disclosures about registered child sex offenders. Another 43 inquiries led to action to protect youngsters, including referrals to children's social care.
The programme was widened yesterday to West Mercia, Bedfordshire, Norfolk, North Yorkshire, Thames Valley, West Midlands, Essex and Suffolk. The rest of England and Wales will be covered by next spring.
The Case For – And Against
For
Some sex offenders are skilled at inveigling themselves into positions of trust, so the checks will help parents to act on suspicions about people with access to their children. Youngsters would be protected while parents would be reassured.
Against
The new law does little more than the current arrangements for monitoring offenders in the community. Yet it threatens to encourage paedophiles to lie low and could encourage vigilantism. It could require police to act in response to gossip and innuendo in the community. Complaints could be prompted by malice, such as a former partner's desire to wreck a new relationship.
Comments