THE pioneering use of lie detectors to monitor sex offenders appears to have been a stunning success, according to a report.

Led by Professor Don Grubin, of Newcastle University, the scheme found that more than four out of ten sex offenders were lying to probation officers.

In 31 cases, the tests uncovered evidence that sex offenders had lied about not committing new offences.

In one case, a 24-year-old man on parole for having sex with a 14-year-old girl admitted to still being in contact with her, and later told police they were having sex.

Information about paedophiles' behaviour, which could be vital in protecting children and others from sex attacks, was obtained in nearly eight out of ten cases.

Prof Grubin, who is based at St Nicholas' Hospital, in Newcastle, said last night: "I have no doubt that a number of offences were prevented because the Probation Service was able to intervene."

The results of the North-East-led scheme, which ended in the summer, is bound to increase pressure on the Home Office to resume lie detection tests as part of the monitoring of sex offenders on parole or out on licence from prison.

Last month, children's charity Barnardo's leaked details of the report and called on the Home Office to introduce compulsory lie detector tests for sex offenders.

The pilot scheme used lie detectors on 350 paedophiles and other sex offenders.

The detectors, which work by measuring minute physical changes in the body, were used to question offenders about whether they had reoffended or breached their parole or community order conditions.

Ten probation services took part in the pilot, but most of the work was carried out in the North-East.

A total of 44 per cent -214 out of 347 -were found to be lying.

No deception was found in only 21 per cent of cases, with the rest either inconclusive or incomplete.

Another offender's lie detector test revealed he was still having sex with his 15-year-old victim.

It also emerged that a 58-year-old internet paedophile was having unsupervised contact with his granddaughter, had taken a girl aged eight or nine into his home unsupervised a number of times and was still using internet chatrooms.

Information provided by the polygraphs led probation officers to increase their risk assessment of offenders in 81 per cent of cases. In a survey of comparable cases in which lie detectors were not used, officers reduced their risk assessments in more than half the cases.

The Home Office said the use of lie detectors was being considered.