Two members of the Advisory Council on the Misuse of Drugs (ACMD) have resigned in protest after the home secretary sacked the UK's chief drugs adviser, Professor David Nutt.
Alan Johnson sacked Professor Nutt on Friday, shortly after he used a lecture to say that cannabis was less harmful than alcohol and tobacco, and that it was upgraded to Class B - against ACMD advice - for political reasons.
In a letter to The Guardian, Johnson said that Nutt was asked to resign "because he cannot be both a government adviser and a campaigner against government policy".
He also hit back against the scientist's frequently quoted assertion that horse riding is more dangerous than ecstasy. "There are not many kids in my constituency in danger of falling off a horse," wrote Johnson. "There are thousands at risk of being sucked into a world of hopeless despair through drug addiction."
Two ACMD members resigned in response. Dr Les King, a former head of drug intelligence at the Forensic Science Service, resigned first, saying that Nutt had been denied his "freedom of expression."
He was followed by Marion Walker head of the substance misuse service at Berkshire NHS foundation trust.
Nutt defended the comments which led to his sacking. He said that it is "imperative that the classification of drugs truly reflects their harms, otherwise injustices may occur and the educational message be undermined".
Writing in the Times, he said: "It seems unlikely that any 'true' scientist will be able to work for this, or future, home secretaries.
"My sacking has cast a huge shadow over the relationship of science to policy."
In an angry interview with Sky News, Johnson insisted that he respected the role of scientists. He said: "I've got enormous respect for the advisory council. I want to meet them very soon. I've got enormous respect for the scientific community.
"They've got to understand that Professor Nutt crossed this line between offering advice ... and then campaigning against the government on political decisions."
The remaining 28 members are meeting on Monday 10 November to plan "collective action". Some commentators are predicting a mass resignation.
