But Labour MP Lynne Jones believes ministers may need to accept some amendments tabled by the House of Lords if a controversial mental health bill is to be given the nod by wavering Labour backbench MPs.

Peers in the House of Lords this week voted by a majority of 106 that mental health patients should have an impairment of decision-making ability before being compulsory treated. The bill does not include such a condition.

Ms Jones, MP for Birmingham Selly Oak, last year tabled an early day motion expressing “misgivings” over the bill.

And although 27 backbench Labour MPs have put their signatures to the motion, if these were turned to opposition votes they would not be enough to overturn the Labour majority in the House of Commons.

"I do not think there will be a major rebellion [by Labour backbenchers]” Ms Jones told psychminded.co.uk

"Although I do think this depends upon the government accepting some of the House of Lords amendments. I hope they will.”

In March last year the government dropped its original bill, first tabled in 2002 and revised in 2004, after a parliamentary select committee slammed it for being “fundamentally flawed”.

In its place ministers last year published a third bill - a series of amendments to the Mental Health Act (1983).

The government argues the new law for England and Wales would both improve care for patients and protect the public by preventing some of the 50-60 annual homicides committed by those diagnosed with a mental illness.

But critics have attacked the bill for lacking detail, threatening civil liberties and would lead to people being detained without therapeutic benefit. Some psychiatrists fear becoming jailers

One key concern over the bill is that, even if a person objects rationally to treatment, psychiatrists can still treat them with force. This is because, unlike present law and in Scotland, the bill contains no condition for detention that a person’s decision-making ability is impaired.

For Dr Tony Zigmond of the Royal College of Psychiatrists, not having a condition of impaired decision-making would be a blatant discrimination against people with mental health problems. People with physical health problems, such as cancer, have the right to refuse treatment.

"People suffering from mental illness should not fundamentally be treated differently from people with physical illness,” he says. “This difference would be exacerbated by this [new] law.”

The bill also contains proposals for community treatment orders (CTOs) whereby patients detained in hospital may be ordered to take their medication while living in the community.

But the government was accused on Wednesday of sitting on a report showing that CTOs neither improve care nor reduce risks to the public.

In the House of Commons shadow health minister Tim Loughton called on mental health minister Rosie Winterton to publish the findings of a Department of Health-commissioned study of how CTOs have worked in 50 countries.

Loughton said the report had been delivered to the Department of Health in the autumn.

He said it concluded that CTOs “have no clear effect on patient outcomes or risk reduction, and that these psychiatric ASBOs have been described as discriminatory by many patient groups, not least those representing black and minority ethnic patients”.

Winterton said the report was being peer-reviewed and would be published in due course.

The Black Mental Health UK group has written to the Commission for Racial Equality claiming the new bill - if brought to the statute books - will break race relations law.