Users in hospital after taking ecstasy powder

Dr Paul Dargan, of Guy's and St Thomas's poisons unit, said his hospitals were receiving many patients who had unintentionally taken the high-strength ecstasy powder.

Many had snorted the drug believing it to be cocaine, when in fact it is 10 times more powerful.

Others had taken it after being told it was ketamine - another favourite substance used by clubbers.

He said the consequences included problems such as hypothermia and expressed his fears about the trend as he gave evidence today to a hearing of the Government's advisory council on the misuse of drugs.

It was meeting to assess whether to downgrade ecstasy - properly known as MDMA - from its current class A status to a class B drug in response to claims that the harm it causes users has been exaggerated.

Dr Dargan warned, however, that growing use of ecstasy powder, which is far more concentrated than the pills more frequently taken, was leading to problems.

"We see a lot of patients who have taken white powder they think is cocaine but is clearly MDMA," he told today's meeting.

"It is a clinically common issue. A significant proportion of the individuals that we see have severe clinical effects."