PROPOSALS to hold dangerous paedophiles in mental hospitals after their release from prison are ''social engineering'' similar to what was done in the former Soviet Union, a leading forensic psychiatrist said yesterday.

Home Office Ministers have said they are considering changing the Mental Health Act to allow sex offenders who have served their prison sentences to be held in psychiatric units.

The move follows widespread public outrage over the release from prison of child killers Robert Oliver and Sidney Cooke. Both helped kill teenage runaway Jason Swift during a homosexual orgy, and both have been judged likely to offend again.

They have been assessed as having ''personality disorders'' but secure mental hospitals have refused to take them. But consultant forensic psychiatrist Dr Chris Jones said hospitals were no place for untreatable paedophiles.

''They're not ill just because they happened to offend against children. If people who have committed these offences have a treatable mental disorder, then by all means let's have them in hospital and let's treat their disorder.

''But it's the sweeping assertion that all these people should be sent to hospital that worries me. Holding them in hospital if we can't do anything for them doesn't do them any good and doesn't do the hospital any good.

''To say here's someone who commits offences, let's send them to hospital, let's get them out of the way, that's what happened in the Soviet Union to people who were unacceptable to society. There the offences were political, but there are parallels. That's not what hospitals should be about.''

The criminal justice system should deal with such people, not the health service, he claimed.

Dr Jones, currently working for the North Wales Forensic Psychiatric Service, has worked at Ashworth Special Hospital on Merseyside.

Doctors from Rampton and Broadmoor special hospitals interviewed Oliver while he was in protective police custody after his release from jail. They judged him to be a ''sexual deviant with a personality disorder'' but that did not allow him to be detained under the Mental Health Act.

The Act specifically excludes sexual deviants from detention under its powers.

Oliver and Cooke were released at the end of their sentences for manslaughter and are not subject to any compulsory supervision.

Oliver is currently a voluntary patient at a medium secure mental unit in Buckinghamshire and Cooke is being held at an unnamed West Country police station for his own protection.

Ministers are also considering ''indeterminate sentences'' for paedophiles which would allow sex offenders still considered a risk to be held in jail after the end of the term laid down by the trial judge. But such powers if introduced would not apply to Oliver or Cooke or anyone currently in jail.