If the purpose of the bill is to improve supervised community treatment and to strengthen protection of the public where there is risk of violence, then vulnerable people must surely be encouraged to seek help - not to hide themselves away.

One safe prediction for 2007 is that the government's latest attempt to update the 1983 Mental Health Act will be the subject of sustained controversy for being what critics are calling a 'lobster pot' bill - one that makes it easier for patients to get into the system than to get out.

When I spoke to Rosie Winterton, the minister responsible for its passage, just before Christmas, she was pretty confident that, after eight years of toil, this time it will be different. 'We'll get the bill through, it's a very different bill,' she assured me, referring to the two previous draft bills, one in 2002, the other two years later, which were savaged by experts and politicians. Each was withdrawn.

But is cheerful Rosie's optimism well founded? Having just read the pre-Christmas second reading debate in the Lords I doubt it. Not even a soothing swansong from outgoing minister Lord Stormin' Norman Warner could dampen widespread criticism.

Quite the reverse. Here was a rare example of a lordly debate heating up over the hours rather than cooling down. By the end of it the Tory spokesman, Earl Howe, and his Lib Dem counterpart, Baroness Barker, were both condemning the latest, shorter and simpler text's persistent lack of balance and of safeguards in harsh terms.

As for Baroness Murphy, what a broadside! The crossbench peer is a psychiatrist by trade and a self-confessed supporter of the Mental Health Alliance, one of many lobby groups which bombarded peers with hostile briefing papers. But was it kind to warn peers tempted to nod off that, on the evidence of such inattention, she and Lord Patel of Bradford (a qualified social worker) could 'get out their pink slips' and have them sectioned under the proposed law?

'We are at one in saying this is a stigmatising, illiberal and yet curiously timid bill. It is a little like a dying wasp, which still has a sting in it,' said Lady Murphy, who says - like many peers - that street-smart young people in the inner cities would be frightened off confiding in doctors and social workers for fear of being 'banged up÷¡®¤ filled with drugs that make you drool and get fat.'

As a layman who, like all of us, has seen his share of mental illness and the daunting, elusive problems of treating it, that strikes me as a wounding charge.

If the purpose of the bill is to improve supervised community treatment and to strengthen protection of the public where there is risk of violence (much exaggerated by the media since the Clunis-Zito murder in London in 1992, peers kept stressing) then vulnerable people must surely be encouraged to seek help - not to hide themselves away.

Some of the criticism of the bill is also unbalanced. No-one disputes that Labour has poured money into mental health since 1997, with marked improvements in many services, some peers paused to acknowledge: Cinderella may not have got to the ball, but she did get a new outfit. And British mental healthcare is better (suicide rates are low) than most in Europe. It is better still under Scotland's new act, add the Anglo-Welsh bill's critics.

Ministers' intentions in this instance are pure, although the need to protect its legal flank against the European court ruling on the Bournewood Hospital case (the autistic man detained against his carer's wishes) is also a pressing motive for legislation.

Labour retains a tendency to pander to tabloid fantasies that a Christopher Clunis lurks round every corner. Even taking the (disputed) expert claim that one such killing takes place each week, a balance is still needed. Should we detain 5,000 people to prevent one such death?

This debate will roar and rumble on. Ministers promise to listen to complaints like the absence of special protection for children, hospital starvation of the elderly, and the disproportionate detention of young Afro-Carribbean men. The absence of adequate safeguards threatens to turn psychiatrists into 'jailers', Labour's Lady Meacher warned.

Yet on two pressing concerns, advocacy rights and a statement of principles guiding treatment, Lord Warner was able to suggest that ministers have some answers up their sleeves. It is more practical and flexible to provide both on a non-statutory basis, he insists. Will they believe him?