The proposals were greeted with anger by civil liberties groups and scepticism by some probation staff who predicted that plans to house up to 4,000 potentially dangerous people in special units would be too costly and controversial to ever get off the ground.
But the Government is determined to plug legal loopholes that allow dangerous people with severe personality disorders to live in the community without supervision. Mr Straw said the public was not being protected properly. Under current mental health laws, people can be detained only if doctors believe their condition is treatable and most professionals believe severe personality disorders are beyond remedy. Psychopaths who have committed a serious crime must be released from prison at the end of their sentence even if they are still judged to be dangerous.
Mr Straw said: "They may have been convicted of crimes carrying only a limited determinate sentence and will have to be released at the end of their sentence, even though they may themselves have warned staff of their certainty of re- committing serious offences on release. The safety of the public is our prime concern."
The human rights group Liberty described yesterday's development as "deeply problematic and quite shocking". The director, John Wadham, said: "Proving you are not dangerous is almost impossible and there is no doubt that some people who are no danger will be locked up."
The Bar Council said Mr Straw risked "opening a can of worms". A spokesman said: "Plans to lock someone up before they have committed a crime need to be examined extremely carefully given the presumption of innocence in our legal system."
But Mr Straw said: "We recognise that detaining people indefinitely on the basis that they pose a danger is a serious step. We will ensure the system of ordering detention involves a robust system of checks and balances covering legal and clinical issues. Once in detention there will be regular quasi- judicial reviews of the justification for continued detention."
Mr Straw's action follows the outcry over the failure to detain Michael Stone, who was convicted of the murders of Lyn Russell and her daughter, Megan, after his pleas for hospital treatment were ignored.
Mr Straw said short-term measures would be introduced. An early-warning system will be set up and a central support group will draw up plans for housing freed psychopaths, which will be subject to a consultation exercise.
Harry Fletcher, of the National Association of Probation Officers, said any such units would encounter big planning problems. He said: "I don't think that this will see the light of day because of the enormous practical problems associated with it."