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.

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.