Ever since eight-year-old Sarah Payne was abducted and killed by convicted paedophile Roy Whiting, the momentum for the UK's answer to "Megan's Law" has been growing.

Ever since eight-year-old Sarah Payne was abducted and killed by convicted paedophile Roy Whiting, the momentum for the UK's answer to "Megan's Law" has been growing.

The launch of new trial legislation similar to that introduced in the US after seven-year-old Megan Kanka was raped and killed by a known sex offender in New Jersey will no doubt be welcomed by campaigners.

However, children's charities expressed caution over the measures and, if the public outcry that ensued when the News of the World chose to publish sex offenders' names in 2000 is anything to go by, such caution is justified.

Even in the US, Megan's Law is not a free-for-all.

Exactly what is and is not available varies from state to state but essentially it allows public access to limited information on the history and whereabouts of high-risk offenders.

Until now such information has been scarce in this country.

Multi-agency public protection arrangements (MAPPA) are panels set up to monitor sex offenders in each region.

In Norfolk there are currently 637 registered sex offenders and there has been a sharp increase in recent years. Of these, 222 live in the central area, 165 in the east and 115 in the west – but that is about as far as it can be narrowed down.

Leanne Boast, spokesman for the county's probation service, said the panel was working effectively – an assertion confirmed by the fact that of the 600-plus offenders in the county, only 11 were returned to custody last year, mostly for minor breaches of their orders.

She added: "The panel involves the police, probation and child-protection officers. There are a huge number of people working very hard to ensure children are safe.

"MAPPA also has liaison officers who work closely with victims who have a say in how a sex offender is managed in the community."

The new system, which will be trialled in north-east Somerset before being rolled out to other selected regions, has been scaled back.

It would have arguably had no effect on the Sarah Payne case, as she was grabbed by a stranger, and is a far cry from the "Sarah's Law" originally envisaged by campaigners.

Parents will not be given the right to information about paedophiles in their neighbourhoods except in very specific circumstances.

Instead the proposals will be almost entirely focused on potential child abuse in the home, and will have little or no impact on "stranger-danger" cases.

Parents, guardians and carers will be able to ask whether a person has child- sex convictions only if that person is able to spend time alone with a child, it is understood.

The system would build on existing laws which already allow police to approach and warn a woman who has begun a relationship with a known paedophile.

Parents may be able to request information about whether paedophiles live on a child's route to school but will not be given names or addresses.

Headteachers may also be informed about serial paedophiles in the area.

A Home Office spokesman said: "Under the existing public-protection legislation, a limited form of disclosure already exists, and the review is looking at how best to focus the impact of any extension to this important principle.

Kidscape children's-charity director Michelle Elliott welcomed the decision not to give wider access to paedophiles' identities. "I never supported that – it would be the road to ruin," she said.

"It would bring vigilantism and did not consider how to decide which paedophiles should be named because they were more dangerous than others."

Barnardo's chief executive Martin Narey said that trials would be "very bad news".

Mr Narey, a former Home Office permanent secretary who ran the prisons and probation services, warned that sex offenders may be driven underground, away from the supervision of probation officers.

He said he was shocked by news of the trials and claimed Barnardo's and the NSPCC had been given assurances that the pilots would not take place.

He said: "This will put children in danger. Our only concern is children and this will put children's lives in danger."

Sir Chris Fox, former president of the Association of Chief Police Officers (Acpo), also expressed concerns about the proposals. He said that offenders could be "potentially punished in the community for the rest of their lives" as a result of the plans, and warned about the dangers posed by vigilantes who might attack suspected paedophiles.

We may have a right to information but we also have a responsibility to use that information correctly. In its proposed form the system appears to remain within safe boundaries – but if pushed any further it could undermine its own purpose and actually place children at increased risk.