Proposals that could see people with severe personality disorders jailed before they commit crimes have been heavily criticised by an alliance of organisations.

The government plans were triggered by several high profile attacks, including the murders of Lin and Megan Russell, carried out by people with histories of psychiatric problems.

But 26 groups, including mental health charity Mind, the Law Society, the Royal College of Nursing and the National Association of Prison Officers, have voiced their opposition to the proposal ahead of the close of an official consultation period.

Concerns centre on the inaccuracy of risk assessment, which could lead to people who are no danger to the public being locked up unnecessarily.

The organisations also say there is no consensus on a diagnosis for what constitutes severe personality disorder. And they say civil liberties issues are raised by the suggestion that non-offenders could be detained even if there is no hope of treating them.

Potentially dangerous

Under the government proposals published earlier in the year, a Medical Legal Panel would be set up with the power to lock up psychopaths on the basis that they were potentially dangerous. The consultation period on the proposals ends on 31 December.

A spokeswoman for Mind said: "We are talking locking people up for an indefinite sentence - for the first time we would be incarcerating people who have not committed a crime.

"We could be locking up five people for every one who might commit a crime - that is not acceptable.

"The concern we are raising with the government is that this is being proposed before they have done the proper research."

And a spokesman for the Royal College of Nursing said: "We have considerable difficulties with the plans. It is something that would need a great deal more investigation."

Sane, the mental health charity, said it shared the concerns of the other organisations, but warned something needed to be done to protect those who posed a risk to themselves and others.

A spokeswoman said: "The status quo cannot continue whereby people with such disorders which are considered `untreatable' are excluded from the mental health services and admitted to the Prison Service only after they have committed an offence.

"Sane believes that a way must be found of providing more chances of treatment and care to this very small group of people. This will involve creating new safeguards."