The scheme comes after the murder of Sarah Payne by a paedophile
A scheme allowing parents to check if someone is a sex offender will be rolled out across England and Wales by March 2011, the Home Office says.
A year-long pilot has already protected 60 children, ministers say. A similar scheme is to be launched in Scotland.
Under the scheme, police can give parents more information about someone who has access to their children.
The biggest category of applicants in the pilot areas was fathers concerned over the new boyfriends of ex-partners.
The sex offender disclosure pilots ran in four areas - Warwickshire, Southampton, Stockton in Teesside and parts of Cambridgeshire - over a year to test how successful they could be at protecting children.
Previously, a parent could alert police to concerns about someone who had access to their children, but there were no clear rules about whether or not they should be told anything if child protection officers discovered cause for concern.
Under the pilots, police were given rules for how and when to disclose, including requiring the parent not to pass the information on to other people in order to avoid panic in a community.
The Home Office said that the take-up for the scheme had been lower than expected, with 315 applications for information over 12 months.
In all, police disclosed information on 32 individuals who had a record of child sex offending or posed a risk in a different way.
One parent contacted the scheme after a neighbour had begun offering sweets to their children. Police confirmed that the individual was a registered sex offender who had been banned from contacting children. He was arrested and remanded in custody for breaching the terms of his release.
While researchers for the Home Office said the low take-up raised a question about whether the scheme was worth it, they concluded that it had strengthened safeguards.
The scheme emerged after a long campaign by Sara Payne, whose daughter Sarah was killed by a convicted paedophile who had been released from prison.
Ms Payne, backed by the News of the World, had called for a British version of a US law that fully discloses the identity and home addresses of convicted sex offenders.
WHO WERE APPLICANTS CONCERNED ABOUT?
17%; Ex-partner's new partner
16%: Family member/friend of family member
9%: Authority figure
8%: Family friend/partner of friend
4%: Neighbour's relative/partner
14%: Other categories
"I am delighted that the years of campaigning and hard work by so many friends and colleagues have provided those who care for children with the right to check that adults who have access to them do not pose a danger," she said.
Ms Payne, who is now the government's official Victims' Champion, said the evaluation had shown the "huge benefits of increased but controlled access to information".
"The input of the police, children's charities and academics to the pilots has ensured consensus has been reached and we are working together to keep children safe."
Home Secretary Alan Johnson said the scheme would be rolled out to 18 additional police forces from August and all others by next March.
"The UK already has one of the most robust systems in the world for the management of sex offenders, the new scheme will build on this ensuring more children are kept safe," he said.
"We've already seen that children are better protected and sex offenders more effectively managed because of this scheme, which is why it is rolling out nationwide."
Liberal Democrat home affairs spokesman Chris Huhne said: "The first goal must be child safety but concerns remain that these measures could drive sex offenders underground.
"In America, where they have Megan's Law, one in five sex offenders has disappeared off the radar, which makes children less safe.
"In the UK, 97% of sex offenders comply with registration requirements. We do not want to risk more sex offenders avoiding the police and probation services."
Shaun Kelly, head of safeguarding at the charity Action for Children, said the project must be properly resourced to make sure it was appropriately monitored.
"The success of this project lies within the commitment from government to properly resource this programme to ensure it is successfully rolled out and, crucially, appropriately monitored," he said.