Home Secretary Alan Johnson addresses the Labour Party Conference on September 29, 2009 in Brighton. (Oli Scarff/Getty Images)
Professor David Nutt was accused of overstepping the mark and straying into politics by criticising the government's tough approach to cannabis, ecstasy and LSD.
Home Secretary Alan Johnson dismissed Nutt, head of the Advisory Council on the Misuse of Drugs (ACMD), after he said the drugs were less harmful than alcohol.
Johnson told the House of Commons on Monday he asked Nutt to resign after he had "lost confidence" in him as principal adviser.
"I asked Professor Nutt to resign...not because of the work of the council but because of his failure to recognise that as chair ... his role is to advise rather than criticise government policy on drugs," he said.
Meanwhile, it emerged on Monday that the Home Office had ordered a review of the council on October 13.
Nutt says the work of the ACMD is no longer tenable and argues that many of its members, who offer unpaid independent advice, back him.
On Sunday, two members of the panel resigned in protest at his removal.
In a letter in Monday's Guardian newspaper, Johnson accused Nutt of "campaigning against government policy" but insisted he was not forced out because of his opinions.
Conservative leader David Cameron said Nutt should have been more tactful and stressed the role of advisers was simply that: to offer advice.
"You clearly need to have scientific advisers...(they) should feel they can give that advice in a clear and unvarnished way.
"That said, all participants in public life ... always have to think about what they are saying and the way in which they are saying (it), whether it has wider ramifications," he said.
Cameron added drug classification should stay as it was.
More to Quit?
Writing in the Times on Monday, Nutt warned more of the remaining 28 ACMD members could quit.
"It seems unlikely that any 'true' scientist will be able to work for this, or future, home secretaries," he said.
Nutt said his sacking had cast a "huge shadow over the relationship of science to policy." He noted two panel experts had already resigned and added: "it seems likely that many others will follow suit."
On Monday, more scientific experts lined up to criticise the government.
John Krebs, former head of the Food Standards Agency and Professor of Zoology at Oxford University was one of them.
"I cannot imagine any reputable scientist wanting to take on David Nutt's job with Alan Johnson as Secretary of State...," he said in statement. "All academics will think hard about offering their advice in such a regime."
