The charge came from David Healy, an expert on psychiatric drugs from north Wales whose warnings that the drugs could cause suicide prompted a major inquiry. That investigation, by an expert working group of the Medicines and Healthcare Products Regulatory Authority, led to the entire class of drugs except Prozac being banned last year from use in children.

The expert working group has gone on to look at suicides in adults taking any of the drugs known as SSRIs (selective serotonin reuptake inhibitors). But Dr Healy says that they are overlooking very important data relating to a set of further dangerous side-effects.

Dr Healy, director of the north Wales department of psychological medicine, says he has seen data from the clinical trials that show even some healthy volunteers - people with no illness at all volunteering to take part in the earliest safety trials of the drugs - became unaccountably aggressive. Their reaction is coded as "hostile" which can include homicidal behaviour and serious aggression.

"I think there is very clear evidence for all of the SSRI group of drugs that in addition to making people suicidal, they can make people homicidal or seriously aggressive and the data have been sitting in the MHRA's files on this issue," he said.

"It is there for children across a range of different problems, it is there for healthy volunteers and a range of adults and the MHRA has paid no heed to this."

The healthy volunteer trials of the British drug Seroxat took place in the late 1980s or early 1990s. Of the 271 fit and well individuals, three became hostile, compared with none on an inactive placebo - a rate of 1.1%, which although small could translate to very many cases among the 50m worldwide who have taken Seroxat over the last 15 years.

The signal from the healthy volunteer trials is supported by data from trials in children on Seroxat for obsessive compulsive disorder (OCD), depression and social phobia. Children taking part amounted to 738 on Seroxat and 647 on placebo. Of those, there were 27 hostile events on Seroxat and only four on placebo. Taking the children with OCD alone, those on the drug were 17 times more likely to become aggressive than those on placebo.

Trials of Seroxat (known generically as paroxetine) for women with pre-menstrual syndrome show a similar pattern, with five hostile acts on the drug and none on placebo.

But, says Dr Healy, the MHRA officials appear not to have picked up the signals from all the separate trials and are failing to see the whole picture.

A number of cases where people have argued their aggressive acts were due to one of the SSRI antidepressants have come to court. In the most dramatic, a US jury in 2001 found that GlaxoSmithKline's drug was partly responsible for the murders committed by Donald Schell. After two days on Paxil (as Seroxat is named in the USA), Schell killed his wife, his daughter and his baby granddaughter before shooting himself dead. GlaxoSmithKline was ordered to pay $8m (£4.5m) to the remaining family members.

GlaxoSmithKline last night denied that its drug caused adults to become hostile, although it acknowledged there had been a problem in the children's trials. "There is no compelling evidence from our clinical trials that Seroxat causes hostile behaviour in adults. When you put the results from all the clinical trials together there is no difference between the rates of hostility for adult patients taking Seroxat and the patients taking placebo, or dummy pill. This data has been shared with regulators including the MHRA," said a spokesman.