Parents may get new powers to check if people with access to their children have paedophile convictions.
The scheme could be rolled out across England and Wales if trials in four regions are successful.
It will allow single mothers to ask police whether a named individual - such as a carer or new partner - has child sex convictions.
Campaigner Sara Payne said the scheme was a step in the right direction but she still wants full disclosure.
Family members or neighbours who regularly look after children could also be checked under the new proposals.
Trials will take place in Cambridgeshire, Hampshire, Cleveland and Warwickshire.
Police and probation services will be able to decide what information to release and there will be careful controls on disclosure, but if children are thought to be at risk it is understood their guardians will be told.
Home Secretary Jacqui Smith stressed the initiative would not see a free-for-all with information given out to anyone who asks.
Under the scheme, parents could register an interest with police about a named individual, such as a new partner or someone who looks after their children, she told BBC1's The Politics Show.
But there would be "tight conditions" over who could register.
"If there were any sex offences recorded against the individual in whom they are declaring an interest, there would be a presumption that they would be disclosed to that person," Ms Smith added.
"It is not a community-wide disclosure. It is not something that some have feared would drive sex offenders underground. It is a sensible way to ensure we have more information out there to protect children in the most effective way."
The move has been hailed as a partial victory for the "Sarah's Law" campaign which called for parents to be allowed to see details of any convicted paedophiles living in their area.
It was named after eight-year-old Sarah Payne who was murdered in 2000 by Roy Whiting.
Sara Payne - Sarah's mother - told BBC News 24 the pilot schemes were a step in the right direction, but there was still a long way to go towards full public disclosure.
"Roy Whiting was previously convicted and I truly believe that if a man like Roy Whiting lives in your community, then you should know that he is there," she said.
"The police and probation service, with all the best will in the world, can't watch every sex offender that there is on the register and watch what relationships they are building, what new areas they are moving into.
"So this is a way of parents taking some of that back."
Communities and local government secretary, Hazel Blears, told BBC1's Andrew Marr Show: "As a politician I have always believed if you share information with people then they are likely to take a more mature, more rational approach."
Paul Cavadino, chief executive of crime reduction charity Nacro said it supported a controlled experiment of providing information to parents, but stringent safeguards were needed to prevent abuse of the system.
He believed ministers were right to resist pressure for a full system of public disclosure, warning it would cause offenders to "go to ground", making it difficult for the police and probation service to keep track of them.
In the US, Megan's Law was named after seven-year-old Megan Kanka who was killed by convicted sex offender Jesse Timmendequas in New Jersey in 1994.
The legislation was adopted in various forms across 50 states. It allows public access to information on the history and whereabouts of high-risk offenders, which supporters say has been a valuable deterrent.
But opponents argue the American law encourages acts of vigilantism and drives paedophiles underground, putting children at greater risk.
Past studies have also shown far fewer paedophiles comply with registration requirements in the US than in the UK.