Alan Johnson dismissed the Government’s chief drug adviser yesterday over his remarks that many drugs were less dangerous than alcohol and cigarettes.

The Home Secretary wrote to David Nutt, chairman of the Advisory Council on the Misuse of Drugs, asking him to resign after he criticised the Government’s decision to reclassify cannabis as a Class B drug, significantly increasing the penalties for possession and dealing.

According to sources Mr Johnson believed that Professor Nutt, after a string of controversial statements, had finally gone too far and feared that he would do so again. “He does not seem to be able to stop himself from straying into politics,” one source said.

Professor Nutt’s the sacking came after he used a lecture at King’s College, London, and a briefing paper to attack what he called the “artificial” separation of alcohol and tobacco from illegal drugs.

In the paper, published yesterday, he wrote: “Alcohol ranks as the fifth most harmful drug after heroin, cocaine, barbiturates and methadone. Tobacco is ranked ninth. Cannabis, LSD and Ecstasy, while harmful, are ranked at 11, 14 and 18 respectively.”

The professor said that smoking cannabis created only a “relatively small risk” of psychotic illness and claimed that those who advocated moving Ecstasy from Class A to Class B had “won the intellectual argument”.

A spokesman for the Advisory Council on the Misuse of Drugs said that Professor Nutt spoke as an academic and not for the council.

Professor Nutt caused alarm at the Home Office this year after suggesting that the risks of taking Ecstasy were no greater than those of frequent horse riding.

A source said: “Anything that appears to downgrade the dangers of drugs is just not acceptable and it should not have been said.”

In his letter Mr Johnson wrote: “I cannot have public confusion between scientific advice and policy and have therefore lost confidence in your ability to advise me as chair of the ACMD.”

Professor Nutt replied: “Whilst I accept that there is a distinction between scientific advice and government policy, there is clearly a degree of overlap. If scientists are not allowed to engage in the debate at this interface then you devalue their contribution to policymaking and undermine a major source of carefully considered and evidence-based advice.”

Public concern over the links between high-strength cannabis, known as skunk, and mental illness led the Government to reclassify cannabis to Class B from Class C last year.

In 2004 David Blunkett, then the Home Secretary, approved the reclassification of cannabis from Class B — which it had been since 1971 — to Class C. The decision to move it back to Class B was taken by Jacqui Smith, Mr Johnson’s predessor.

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