Three years ago, Anthony Hardy killed and dismembered two prostitutes in north London. The "Camden ripper", as he became known in the press, then dumped the women's body parts in dustbins near his home. Only six weeks before, Hardy had been discharged from a mental hospital in spite of staff concerns that he might pose a threat to the public.

Ministers are now preparing legislation that would allow detention of people with a dangerous personality disorder such as Hardy's, including some who have not committed a serious crime.

In the opinion of the mental health minister, Rosie Winterton, "although the majority of mental health patients pose no danger to themselves or others, the government has a duty to protect people with serious mental health problems from harming themselves or other people".

But the bill, which is due to be introduced into parliament at any time, has provoked the anger of a parliamentary committee as well as the sector's professionals, charities and service users.

The chairman of the joint committee on a previous draft of the bill, Lord Carlile of Berriew, said in July that it "does not do enough to protect patients' rights". And the chief executive of Sane, Marjorie Wallace, warns that measures such as compulsory treatment in the community could be just "a temptingly cheap alternative to inpatient or other skilled 24-hour care".

So far, ministers have refused to back down.

But Britain is not the only country to be having this debate. In Sweden, a country where the protection of individual rights has always been high on the agenda, even more drastic measures are being considered.

The Swedish government is planning a series of proposals that it believes will protect the community at large from individuals with a dangerous mental illness who could pose a threat to the public.

One of the most controversial proposals involves the Swedish security service (Säpo), the Nordic country's equivalent of MI5. Säpo wants doctors to break their confidentiality if patients tell them, say, that they want to kill the king, the prime minister or any of the other 400 dignitaries the service is in charge of protecting.

"It is a great hindrance in terms of threat assessment," explains Anders Thornberg, communications director at Säpo. "This should not be forbidden. We need this information if we want to protect people effectively."

The measure comes as a direct result of the 2003 murder of the Swedish foreign secretary, Anna Lindh, who was shopping unguarded at a Stockholm department store when she was repeatedly stabbed. Her killer, 27-year-old Mijailo Mijailovic, claimed at his trial that voices in his head told him to attack her. The supreme court, however, rejected that he was mentally ill at the time of the murder and ruled that his psychological disorder was not of a psychotic nature. Mijailovic is now serving a life sentence in jail.

Nevertheless, a government inquiry into the murder of Ms Lindh concluded last year that Säpo should be able to obtain information from the health and medical services that is "of direct and decisive importance for their threat assessment", even if this breaks professional secrecy. Mr Thornberg reckons that this will concern a small number of patients. "We are only talking about 10 to 20 cases every year," he says.

But within the mental health community, the proposal is unpopular. "People say all kinds of things when they are in a psychotic state and it is very difficult to separate what is fantasy and what is reality," says Jonas Dahl, legal adviser for the National Association for Social and Mental Health, the main organisation representing patients and their families. "People sometimes don't say what they are going to do. Take Mijailovic: he never declared he was going to hurt someone."

Mr Dahl also points out another risk: "People will be less likely to seek treatment if they fear information about them is going to be passed on to Säpo."

Another proposal that is provoking an outcry is the creation of a national register of individuals in secure psychiatric care. It would contain current information about every patient being held, including details about their diagnosis, period of care, if they try to escape or are put in solitary confinement, if they are restrained or are drug abusers.

"We want to collect this data for research purposes only so that we know whether there are deficiencies in the care of patients," explains Helena Silfverhielm, medical adviser for the Board of Health and Welfare, the supervisory authority for social and health services. "This is for the own safety of patients and the protection of the community. People are already registered if they go to the surgical department of a hospital. This is just another step."

Ms Silfverhielm says that only the statistics will be made available. Information about individuals would not be shared with anyone outside, and would only be seen by one or two people internally.

Mr Dahl is doubtful. "For over 50% of patients who undergo forced treatment it only happens once in their lives, after a big crisis such as a divorce, and they never come back," he counters. "It would be terrifying for our members if the register would be open, for instance, to the police."

In Britain, the mental health community is even clearer in its opposition to the suggested Swedish approach.

"We would be totally opposed to a national register and would have grave reservations about reporting possible threats to MI5," says Tim Spencer-Lane, chairman of the policy group for the Mental Health Alliance - the coalition of over 60 organisations, including Mind, Sane and the Law Society, which is campaigning against the mental health bill.

"Clinicians can break confidentiality if they believe there is a credible threat against a person. But it would be quite bizarre and very draconian to report it to MI5.

"The government tried to float the idea of a national register of parents who could pose a risk to their children. Risk was defined as widely as having been diagnosed with a mental illness," he explains. "There was a huge backlash then and I think there would be huge problems if something of the kind was considered."