This article is more than 10 years old

This article is more than 10 years old

Alan Johnson, the home secretary, has sacked Professor David Nutt as senior drugs adviser after the scientist renewed his criticism of the government's decision to toughen the law on cannabis.

Johnson wrote to Nutt saying he no longer had confidence in him as chairman of the Advisory Committee on the Misuse of Drugs (ACMD) and asking him to consider his position.

Nutt had accused ministers of "devaluing and distorting" the scientific evidence over illicit drugs by their decision last year to reclassify cannabis from class C to class B against the advice of the ACMD.

A Home Office spokesman said: "The home secretary expressed surprise and disappointment over Professor Nutt's comments which damage efforts to give the public clear messages about the dangers of drugs."

In his reply, Nutt said: "If scientists are not allowed to engage in the debate then you devalue their contribution to policymaking."

The sacking is likely to raise concerns among scientists over the independence of advice to the government and may trigger further resignations. The Home Office describes the ACMD as an independent expert body that advises on drug-related issues, including recommendations on classification under the 1971 Misuse of Drugs Act.

It is not thought that the home secretary spoke directly to Nutt before requesting his resignation in writing.

Nutt told the BBC: "I think the issue is whether I am straying into the realm of policy. I personally don't think I was."

The decision follows the publication of a paper by the Centre for Crime and Justice at King's College London, based on a lecture Nutt delivered in July. He repeated his familiar view that illicit drugs should be classified according to the actual evidence of the harm they cause and pointed out that alcohol and tobacco caused more harm than LSD, ecstasy and cannabis.

He also argued that smoking cannabis created only a "relatively small risk" of psychotic illness.

The shadow home secretary, Chris Grayling, backed Johnson's decision. "This was an inevitable decision after his latest ill-judged contribution to the debate but it is a sign of lack of focus at the Home Office that it didn't act sooner given that he has done this before."

Richard Garside, director of the centre for Crime and Justice Studies at King's College London, accused Johnson of undermining scientific research. He said: "The message is that when it comes to the Home Office's relationship with the research community honest researchers should be seen but not heard."

Phil Willis, the Lib Dem MP who chairs the Commons science and technology committee, said independent advice to the government was essential and the sacking of Nutt was "disturbing if an independent scientist should be removed for reporting sound scientific advice".

The charity DrugScope's director of communications, Harry Shapiro, said: "The home secretary's decision to force the resignation of the chair of an independent advisory body is an extremely serious and concerning development and raises serious questions about the means by which drug policy is informed and kept under review."

1970 Special class B category, half way between "hard" and "soft" drugs, created for cannabis as a compromise between Labour home secretary, James Callaghan, who believed it was as dangerous as heroin, and a "student faction" in cabinet who did not.

1978 Advisory Council on Misuse of Drugs recommends downgrading cannabis from class B to C. Labour home secretary Merlyn Rees rejects advice.

2002 ACMD looks again at status of cannabis at request of home secretary David Blunkett, who accepts recommendation to downgrade it from B to C, on grounds it is less harmful than class B drugs such as amphetamines.

2008 Home secretary Jacqui Smith rejects advice from ACMD to keep cannabis at class C after a ­ review concludes that evidence of a link between mental illness and stronger strains of cannabis remains weak.

February 2009 Smith vetoes ACMD recommendation that ecstasy be downgraded from class A after it reviewed 4,000 papers on the subject.

October 2009 Alan Johnson sacks Professor David Nutt as ACMD chair.

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