Victims who are made to talk about the pain and shock of their accidents are three times more likely to suffer long-term problems than those who receive no counselling.
The findings have been made by a team of psychiatrists based at the Whitchurch hospital in Cardiff who monitored the recoveries of 110 burns victims.
Similar findings were made by an Oxford-based research team working with victims of road accidents.
The researchers say that the widespread belief that debriefing is beneficial may be misplaced.
They argue that it is better to leave victims alone until they start to show symptoms of trauma rather than exacerbate the problem with shock therapy.
In the Cardiff study, half of the victims agreed to undergo an hour of counselling with a therapist within a week of their burns accident.
They were asked to describe the events leading up to the accident, the pain they felt and any nightmares they had experienced after the incident.
The victims, aged between 16 and 65, had suffered in a range of incidents from chip-pan fires to industrial accidents. Some had up to 32 per cent burns.
Those taking part in the study were interviewed after three months and again after 13 months to see if they had suffered any long term psychiatric problems.
The researchers found that 26 per cent of those who had been asked to talk to therapists about how they were burned had gone on to suffer post- traumatic stress disorder (PTSD).
The symptoms of PTSD include recurring nightmares, a sense of personal isolation, disturbed concentration, irritability and depression.
By comparison, only 9 per cent of those who had not been given counselling later had PTSD. The results are to be published shortly in a scientific journal.
Dr Jonathan Bisson, the psychiatrist who led the research team, said: "The findings were that the debriefing had not prevented psychological problems at all. In fact, those that received the debriefings fared worse than those who received nothing at all. It is possible that the debriefing actually contributes to the patient getting PTSD," he said.
Burns victims could still benefit from undergoing therapy but it needed to be done as part of a long-term controlled programme. "The best policy appears to be to wait until the problems occur and then treat them with a prolonged course of therapy."
The Cardiff findings were supported by research carried out with road- accident victims by Dr Richard Mayou and Dr Mike Hobbs at Warnford psychiatric hospital, Oxford.
They followed the recoveries of more than 100 traffic accident victims who needed treatment at the John Radcliffe hospital, Oxford. Half the victims were given a debriefing.
Dr Hobbs, a consultant psychotherapist, said: "There's a bandwagon assumption that debriefing is a good thing. The reality is that in our study it did not reduce or prevent PTSD." He said the most vulnerable people to PTSD were those accident victims who formed the opinion that they were at risk of serious injury, even if they were not.
Others at risk were those who already had psychological problems or a psychiatric illness or those who were suffering from other forms of stress, such as a bereavement, at the time of their accident.
Dr Hobbs said that some victims valued the experience of the debriefing even though it had been shown not to prevent PTSD.
A third study by researchers at St George's hospital, south London, found that debriefing was also ineffective in preventing trauma in assault victims.Reuse content