It will say that a significant proportion of these deaths could have been avoided, had it not been for health service failures or legal loopholes.

Almost a third of the killings were committed by people judged by mental health staff not to be a risk to the public in the week before the killing.

One in six deaths were attributed to the failure to ensure that the mentally ill patients continued to take their medication once they had been released into the community.

Professor Louis Appleby, who headed the inquiry, said not enough had been done since the high-profile killing of Jonathan Zito in 1992 by a schizophrenic patient let out into the community.

The government has been promising new legislation for the past seven years but, until the publication last month of a mental health bill, has failed to implement any reforms.

Among those killed in that time are Brian Dodd, a retired accountant stabbed to death by a paranoid schizophrenic after care workers failed to check on the patient’s whereabouts every 12 hours, as required, and Detective Constable Michael Swindells, who was killed by another mental patient whose health workers did not check he was taking his drugs.

Last month an inquiry into the murder of Denis Finnegan, a retired investment banker, in Richmond Park, southwest London, found one of the reasons for his death was his killer’s failure to take his medication for paranoid schizophrenia.

Professor Anthony Maden, a psychiatrist at Imperial College London, who works at Broadmoor high-security hospital and advises the Home Office, said: “If you have close involvement with just one of these cases, you never ever want to see it again.”

Ministers will now push ahead with plans to introduce new community treatment orders — so-called mental-health Asbos — to force mental patients to take drugs after being released from hospital. Those refusing to do so risk being sectioned. The system for checking up on patients in the community will also be strengthened in the new year.

The National Confidential Inquiry into Suicide and Homicide by People with Mental Illness found that 5% of all killings were committed by schizophrenics, who make up 1% of the population.

Appleby, who is also the government’s national director for mental health, said: “We have to acknowledge how many [killings] might have been prevented had we acted earlier. Quite a lot of these cases have preventable elements. For example, 25% of patients committing homicide had stopped taking their medication.

“We looked at how many might be prevented by the community treatment orders — how many patients were detained, subsequently stopped their medication and then went out to kill someone. The answer is 16% — one in six of the 52 homicides.”

Appleby said the inquiry had also uncovered a “big issue about risk recognition and management”. “What we have done is look at the timing of the last contact with [mental health] services,” he said. “In 29% of the 52 homicides, the last contact was in the week before the incident. In almost all cases the staff rated the risk as low or absent . . . the risk was underestimated.”

The study said 18 murders were committed by people with a history of violence who were not getting adequate treatment.

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