Home Secretary Theresa May hailed an "important step forward for child protection" as Sarah's Law, which allows parents to check if someone has a history of child sex offences, was rolled out nationally today.
Mrs May said the programme, which followed the abduction and murder of eight-year-old Sarah Payne by convicted sex offender Roy Whiting 10 years ago, will also help police manage known sex offenders more effectively.
The Home Office scheme gives a parent or guardian the right to check with police if anyone with regular unsupervised access to their children has a criminal conviction for child sex offences.
Mrs May said: "The roll-out of this scheme is an important step forward for child protection in this country.
"Being able to make these checks reassures parents and the community and more importantly keeps children safer.
"Not only will it help parents, carers or guardians ensure that their children are safe, but it also assists the police in managing known sex offenders living in the community more effectively.
"The start of the nationwide roll-out will mean even more children will be protected from potential harm."
Sarah Payne's mother, Sara, was crowned the government's Victims' Champion after her ceaseless attempts to bring in the law based on the so-called Megan's Law in the US which allows the publication of names, addresses and pictures of paedophiles in some states.
More than 60 children were protected from abuse during the pilot scheme which started in four areas of the UK in September 2008, the Home Office said.
Almost 600 inquiries to the four forces involved in the pilot led to 315 applications and 21 disclosures about registered child sex offenders.
A further 43 cases led to other safeguarding actions, including referrals to children's social care, and 11 general disclosures were made regarding protection issues linked to violent offending.
The move was broadly welcomed by politicians and campaigners.
Chief Constable Paul West, of the Association of Chief Police Officers (Acpo), said: "These new arrangements are a major development in safeguarding children.
"They empower members of the public to initiate action aimed at protecting children and will help to increase public confidence in the police and other responsible authorities as part of their role in monitoring sex offenders.
"In addition to enabling parents, carers or guardians to take active steps to protect their children, some of the cases that have arisen during the pilots have included extended family members and neighbours who have raised concerns.
"Their interventions have undoubtedly resulted in children being protected from potential abuse."
But some charities warned that the scheme could backfire by driving paedophiles underground.
Diana Sutton, of the NSPCC, said: "It's good that the disclosure pilots have helped to protect children.
"However, 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."
The introduction of the Child Sex Offender Disclosure Scheme follows the trial that took place in Cambridgeshire, Cleveland, Hampshire and Warwickshire.
Today, the scheme was rolled out to eight other force areas - West Mercia, Bedfordshire, Norfolk, North Yorkshire, Thames Valley, West Midlands, Essex and Suffolk.
A further expansion is planned for the autumn, with Northamptonshire, Staffordshire, Sussex, Leicestershire, Wiltshire, Cheshire, Durham, Northumbria, Dorset, Lincolnshire, Surrey and Gloucestershire joining the scheme.
It will be rolled out to other forces by spring next year.