Convicted paedophiles could be forced to take lie detector tests to ensure they stay away from children, under plans by Home Secretary David Blunkett.
The tests are designed to ensure public safety from paedophiles
He wants compulsory testing in Sussex, Northumberland and the West Midlands - currently piloting voluntary tests.
Probation officers would ask offenders whether they had had contact with children since their release from jail.
But reports suggest there is concern among some Cabinet members over the use of the US-style polygraph test.
'Ensuring public safety'
A Home Office spokeswoman said the tests would accompany other methods, such as electronic tagging, to monitor the behaviour of offenders following their return to the community.
The Home Office spokeswoman said: "(Lie detector) testing is carried out purely on a voluntary basis in the pilots.
"We are not talking about a countrywide expansion of the scheme.
"What we are looking for now is to make these pilots mandatory so that we can fully assess the effectiveness of lie-detector tests in helping to monitor sex offenders and ensure the safety of the public."
Mr Blunkett has told the Cabinet he is hoping to bring in legislation to extend the current voluntary trial in several parts of England.
But reports on Sunday suggested that the proposal to move from voluntary to compulsory testing had sparked concern in the Cabinet.
The Sunday Times quoted Trade Secretary Patricia Hewitt - a former head of the National Council for Civil Liberties - as requesting "further evidence" before a decision is reached on whether to push ahead with the necessary legislation.
Polygraphs - which measure changes in breathing, heart-rates and sweat in response to questioning - are considered to be only around 90% accurate, which could lead to fears over their authority in cases of increased monitoring or tagging of paedophiles.
Mr Blunkett is reported to have accepted his proposals are "not without controversy" and to be consulting Attorney General Lord Goldsmith on the legal
Tests would not be used to gather evidence for court cases and offenders would not be returned to jail purely on the basis of polygraph results.
It is believed that the prospect of compulsory
tests would act as a deterrent against breaches of offenders' terms of release.
The Sunday Times report includes extracts from what it says is a leaked letter from Mr Blunkett to
Deputy Prime Minister John Prescott on 20 July.
The Home Secretary asks for Cabinet approval for legislation, which he said would be "an additional weapon in the armoury against sex offenders".
Contact with children
He added: "I accept that this is not without controversy. Given the controversial nature of these proposals, I am consulting Peter Goldsmith."
So far voluntary trials in Northumberland, the West Midlands and Sussex have reportedly been judged a success.
In one trial, 32 offenders volunteered for tests and a third admitted having unsupervised contact with children, according to the Sunday Times.