A former Home Office minister has said it might not be possible to get the Parliamentary Labour party to agree to a British version of Megan's Law.
Angela Eagle said she did not know if the law would protect children
Labour MP Angela Eagle told BBC One's Sunday AM programme it may be difficult to pass a law allowing communities to know if paedophiles are living nearby.
Ms Eagle said she was not convinced that Megan's law protected children.
Megan's Law was introduced in the US after Megan Kanka, 7, was raped and strangled by a convicted paedophile.
Campaigners in the UK want to introduce a similar law allowing people to know if convicted paedophiles were living in their community - sometimes called Sarah's Law, named after Sarah Payne, who was murdered in 2000 by Roy Whiting.
Ms Eagle said: "I think there would be difficulty in the Parliamentary Labour Party if attempts were made to introduce laws like the education reform which are based on assertion, not evidence. So we've got to look at the evidence - at what works to protect children.
The News of the World has been campaigning for Sarah's Law
"Above all we need to protect children. I am not convinced Megan's Law does it.
"What often happens is that paedophiles are targeted, but also people who are odd or don't fit in, people are accused of being paedophiles and then also targeted and subject to vigilante action."
Under the Megan's Law system, states list offenders' details on the internet, allowing parents to enter their zip code (post code) or a name, to check if anyone on the register has moved in nearby.
Sarah's Law would differ in that police would control access to who could view the information.
Sir John's support
Former Metropolitan Police Commissioner Sir John Stevens pledged his support for the law in an article published in the News of the World newspaper.
He said the UK version of the law would allow police to vet those who asked for information on paedophiles and would cut down the risk of vigilante action.
Sir John Stevens is backing Sarah's Law
"You'd have to be a parent or a child carer, on the electoral roll with a permanent address, have a clean criminal record and no history of violence.
"That's very different from the American system. Much safer, much more controllable," Sir John wrote.
He said he believed many others in the UK's police also supported Sarah's Law.
The News of the World reported on Sunday it had found two convicted paedophiles filming children in a park in Guilford, Surrey, with a video camera.
It claimed the two men were David Ramsden, 73, a convicted child rapist who is awaiting sentencing, and child rapist Vincent Graham, 59, who was jailed for 10 years in 2001 for child rape.
It said the men, who were both living in the same hostel, should not have been left unsupervised.