The Home Secretary has defended his decision to sack the government's chief drugs advisor as the row over the decision escalates.

Writing in the Guardian, Alan Johnson stressed that Professor David Nutt had not been asked to resign because of his views, which he said "I respect, but disagree with".

However, he said that the professor "cannot be both a government adviser and a campaigner against government policy."

In a statement to the Commons on Monday, Mr Johnson said the reason for Professor Nutt's sacking was "his failure to recognise that his role is to advise rather than criticise"

He also said that he had "lost confidence" in the professor's ability to be his principle adviser on drugs.

Professor Nutt was sacked on Friday after he had said that cannabis was less harmful than tobacco and alcohol and had been upgraded to a Class B drug for political reasons.

The Liberal Democrats criticised the decision, with the party's home affairs spokesperson Chris Huhne saying: "Ministers have constantly ignored the advice of experts when it comes to drug policies and pressed ahead with their own prejudices.

"If ministers care so little for independent scientific advice, they should save public money by sacking the entire group of experts and instead appoint a committee of tabloid editors."

The row has so far resulted in two other members of the Advisory Council on the Misuse of Drugs (ACMD) quitting their posts in protest over Professor Nutt's sacking, and he has warned that there could be further resignations.

Writing in The Times, the professor said that more of the council's remaining 28 members could leave, saying: "It seems unlikely that any 'true' scientist will be able to work for this, or future home secretaries."

The other council members are due to meet on November 10 to discuss the issue. They have sent a letter to the Home Secretary expressing "serious concerns" over his decision to sack Professor Nutt.

(KMcA/BMcC)