A controversial study which claimed that ecstasy users ran a high risk of brain damage similar to that seen in Parkinson's disease has been withdrawn because the tests used the wrong drug. 

In a short, terse announcement this weekend, the US journal Science revealed that the team of scientists who made the claim had now admitted that their findings were completely false because of a labelling error. 

The neurologists, from Johns Hopkins University in Baltimore, Maryland, said the squirrel monkeys and baboons used in their tests had actually been dosed with methamphetamine, otherwise known as speed - not the MDMA compound used in ecstasy.  Dr Jon Cole, a leading British expert on ecstasy, said that this "amazing" admission would cause "irreparable damage" to drugs education in the UK and increase the scepticism of drugs users about future ill-health warnings. 

"Why should any ecstasy user believe scientists after this?" he asked.  "Even what we do know about ecstasy will now be ignored because users are looking for a reason not to believe us."

The US team had originally claimed that their results, published by Science last September, proved that even one large dose of ecstasy could cause permanent brain damage, leading to tremors, stiffness and slowed movements, similar to Parkinson's. 

These claims caused intense controversy among doctors and other scientists, but were welcomed by anti-drugs campaigners.  They stepped up demands for tougher police action against drug-taking and club culture. 

Alan Leshner, the former director of the US National Institute on Drug Abuse and chief executive of the American Association for the Advancement of Science, which publishes the journal, claimed this proved that even casual users were "playing Russian roulette with your brains". 

The row had added significance as the study was published three weeks after a study by senior British psychologists found no evidence that ecstasy use caused long-term harm, and said many studies criticising the drug were flawed or inconclusive. 

In their retraction, Dr George Ricaurte and four of his colleagues admitted that they had failed to repeat the results of their ecstasy study. 

"Multiple subsequent attempts to reproduce the original findings with systemically administered doses of MDMA identical to those used in the original study were also unsuccessful, under a variety of laboratory conditions," they said.