Moves to introduce compulsory lie detector tests for convicted paedophiles have prompted concern among members of the Cabinet, according to reports.

The Home Office has confirmed that it is looking to introduce compulsory testing in Sussex, Northumberland and the West Midlands.

Trials are already underway in these areas, with the tests conducted on a voluntary basis.

Home secretary David Blunkett was reported on Sunday to have told the Cabinet that he wants to introduce legislation to extend the current pilot tests.

However, while probation officers would question offenders on whether they had been in contact with children, they would not be returned to prison purely on the basis of the results.

The Home Office said the tests would be used as a "limited management tool" to monitor the behaviour of offenders, along side other methods such as electronic tagging.

"Testing is carried out purely on a voluntary basis in the pilots," said a department spokesman.

"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."

Cabinet concern

The news came amid reports that senior members of the Cabinet were concerned about the plans.

Reports in the Sunday Times suggested that trade and industry secretary Patricia Hewitt had called for "further evidence" before a decision is made to introduce legislation.

In a letter to deputy prime minister John Prescott on July 20, seen by the newspaper, Blunkett argued that the move would be "an additional weapon in the armoury against sex offenders".

"I accept that this is not without controversy," he added, saying he was consulting with attorney general Lord Goldsmith on the plans.

Polygraph tests are considered to be accurate in around 90 per cent of cases, but the voluntary trials conducted so far are believed to have been a success.

In one trial in which 32 offenders volunteered for tests, a third admitted having unsupervised contact with children, reported the Sunday Times.