It was billed as the one of the most dramatic warnings the world has ever received over the dangers of ecstasy. A study from one of America's leading universities concluded that taking the drug for just one evening could leave clubbers with irreversible brain damage, and trigger the onset of Parkinson's disease.

The study, published in the eminent journal Science last September, had an immediate impact. Doctors and anti-drug crusaders spoke of a 'neurological time bomb' facing the young. Others suggested that taking one of the tablets was the equivalent of playing Russian roulette with the brain, and demanded tighter 'anti-rave' laws to deal with it.

But today, scientists are facing up to the humiliation of admitting that the stark results they reported in the study were not a breakthrough but a terrible, humiliating blunder.

The study was based on the fact that laboratory monkeys and baboons had a severe reaction to the drug when it was injected in small doses. But it emerged this weekend that the vials of liquid did not contain ecstasy. Instead, the animals received a dose of methamphetamine, or speed - a drug widely known to affect the body's dopamine system. The tubes had somehow been mislabelled by the supplier.

In this week's Science, the scientists will publish a retraction of their original study, reigniting the row over the role of those who investigate ecstasy, as well as the real risks or benefits of the drug.

In academic circles, the mistake is a severe embarrassment to Johns Hopkins University, in Baltimore, Maryland, which attracts millions of dollars of research funding from both government and companies. Questions are already being asked about whether the lead researcher, George Ricaurte, was inherently biased against the drug.

The mistake only came to light when follow-up tests gave conflicting results. The original study reported how two out of 10 animals died quickly after their second or third dose. Six weeks later, the dopamine levels in the surviving animals were down by 65 per cent, leading Ricaurte and his colleagues to conclude that it could provoke the onset of Parkinson's, which is linked to a loss of dopamine-producing cells.

He said at the time: 'It is possible that some of the more recent cases of suspected young-onset Parkinson's disease might be related, but that this link has not been recognised.'

When the study was published last September, a chorus of experts saw it as evidence of drug damage. Professor Colin Blakemore of Oxford University, soon to be the new head of the Medical Research Council, said it provided further evidence that 'ecstasy can be toxic to nerve cells'.

Dr Alan Leshner, chief executive of the American Academy for the Advancement of Science, which publishes the journal, went as far as to describe taking ecstasy as playing 'Russian roulette' with brain function.

He added: 'This study showed that even very occasional use can have long-lasting effects on many different brain systems. It sends an important message to young people - don't experiment with your brain.'

Yesterday, Ricaurte was attempting to put a brave face on the calamity. He is under attack from all sides, and has already been accused of rushing his study into print because Congress was looking at a bill known as the Anti-Rave Act, which would punish club owners who knew that drugs such as ecstasy were being used on their premises.

Ricaurte has denied political bias. He said yesterday that his laboratory made 'a simple human error', adding: 'We're scientists, not chemists.' Asked why the vials of liquid were not checked before being used on the animals, he replied: 'We're not chemists. We get hundreds of chemicals here - it's not customary to check them.'

It is unusual for Science to have to publish a retraction, but that is exactly the right thing to do, according to Joe Collier, professor of medicines policy at St George's Hospital Medical School.

'People must realise that mistakes are made, even by scientists,' said Collier. 'It is embarrassing - a lot of self-questioning will be going on over there - but it's important we learn from this.'

Over the past five years, controversy has raged about the real dangers of ecstasy, a drug which is taken by around a million clubbers in Britain every weekend.

Some studies have suggested that ecstasy has no long-term impact on the levels of the hormone serotonin in the brain, while others have suggested that it leaves clubbers feeling depressed and unable to concentrate.

The controversy is not likely to go away quickly while the scientists themselves are caught up in such a political and academic minefield.

jo.revill@observer.co.uk