Blunkett comes to defence of proposals to lock up the mentally ill indefinitely

David Blunkett is to defend plans for psychopaths to be locked up indefinitely amid signs the proposals will fail to pass through Parliament.

Labour MPs will join a coalition of Tories, Liberal Democrats and independent peers in an attempt to block the Mental Health Bill to be announced in the Queen's Speech next month. The Department of Health has reservations about the proposed powers to force people with untreatable illnesses into mental hospitals, but Mr Blunkett is determined to press ahead.

Speaking to the mental health charity the Zito Trust today, the Home Secretary will say his Bill will stop the victims of people suffering mental illness being treated as "second class citizens". Mr Blunkett will insist his measure will strike the right balance. He will say: "The right of safety for victims and the community with the rights of individuals with mental health problems are complementary aims, not opposing aims."

Privately, ministers are bracing themselves for a rough ride in Parliament and are believe that if the proposals are not amended, they will not be passed by the House of Lords.

Senior Labour MPs including David Hinchliffe, the chairman of the Commons Health Select Committee, have expressed grave reservations. They are worried by plans to allow the compulsory detention of psychopaths or people with "dangerous and severe personality disorders" that are not considered to be treatable.

The Home Office, which will jointly sponsor the bill with the Department of Health, wants to push through measures to clamp down on dangerous people such as Michael Stone, who murdered Lin Russell and her daughter Megan in 1996, and Christopher Clunis, a schizophrenic who stabbed Jonathan Zito to death on a tube platform in an unprovoked attack.

Fifty organisations including the main mental health charities, the Royal College of Pychiatrists and the British Association of Social Workers have expressed concerns about allowing doctors to force people with mental illnesses to take medication. The Bill will also allow the compulsory detention in a mental hospital of "any disorder or disability of mind or brain which results in mental impairment or disturbance of mental functioning".

Charities say the plans are draconian and vague and could be used against consistently obstreperous, violent and dysfunctional teenagers.