Another adviser to the government on drugs policy has resigned over claims of political interference.
Eric Carlin has announced he is stepping down from the Advisory Council on the Misuse of Drugs (ACMD), partly because of how quickly ministers pushed through a ban on mephedrone.
The home secretary, Alan Johnson, announced last week that the drug will become a class B prohibited substance. The decision was made within days of media reports linking it to the deaths of young users.
In a letter reproduced in full on Carlin's blog, he told Johnson: "We had little or no discussion about how our recommendation to classify this drug would be likely to impact on young people's behaviour. Our decision was unduly based on media and political pressure."
A Home Office spokesman confirmed the resignation. He called it "regrettable" but said: "It does not impact on our plans to ban mephedrone and the other substances as soon as parliamentary time allows."
Carlin, 47, has a long background in drug advice charities. He is the seventh member of the ACMD to step down since the controversial sacking last October of its chairman, Professor David Nutt. Nutt had criticised the government for rejecting recommendations on the classification of cannabis and ecstasy. He said the latter drug was less harmful than alcohol.
In his letter, Carlin said he decided to stay on after Nutt's departure to see whether the ACMD could still do some good work but now had "no confidence" of this.
The focus on mephedrone had been at the expense of other issues, he said, particularly prevention and work with young people.
"We need to review our entire approach to drugs, dumping the idea that legally sanctioned punishments for drug users should constitute a main part of the armoury in helping to solve our country's drug problems. We need to stop harming people who need help and support.
"As well as being extremely unhappy with how the ACMD operates, I am not prepared to continue to be part of a body which, as its main activity, works to facilitate the potential criminalisation of increasing numbers of young people."
Nutt said he supported Carlin's decision, saying the mephedrone ban had been pushed through by the government "to the end of trying to appease the media and political opponents".
Nutt told Sky News: "The meeting this week was rushed through so that the chairman could leave to do a press conference when the home secretary wanted to do a press conference. It's a travesty about a proper discussion, about the proper way in which you should deal with an important issue like mephedrone."
Johnson's political opponents sought to capitalise on Carlin's departure. The shadow home secretary, Chris Grayling, called the government's relationship with the ACMD "utterly shambolic", while his Liberal Democrat equivalent, Chris Huhne, accused Johnson of "pandering to tabloid newspaper editors".