The Government was bitterly divided last night over the sacking of the Home Office’s chief drugs adviser after its Science Minister said that he was appalled by Alan Johnson’s decision.

Lord Drayson, the Science and Innovation Minister, wrote to No 10 asking if the Prime Minister could undo the Home Secretary’s decision to dismiss David Nutt.

He said that he had not been consulted by Mr Johnson before Professor Nutt was sacked for having said that alcohol and tobacco were more dangerous than Ecstasy and LSD, and for questioning the decision to downgrade cannabis. In an e-mail to Nick Butler, the Prime Minister’s policy adviser, Lord Drayson wrote: “Alan did this without letting me know and giving me a chance to persuade him. It’s a big mistake. Is Gordon able to get Alan to undo this? As ‘science champion in Government’, I can’t just stand aside on this one.”

According to The Sun, which obtained a series of e-mails written by Lord Drayson, the minister said he was “pretty appalled” at the decision.

Last night Lord Drayson said: “My comments in the e-mail exchange were my immediate reaction to what had happened, without full knowledge of all the facts. I talked to Alan Johnson and he has assured me of the importance he attaches to scientific advice and his respect for scientific advice while being the person who has to make the final difficult decision.”

The resignation of a key member of Britain’s drugs advisory panel after the sacking of Professor Nutt has left ministers powerless to develop or update drugs policy.

The departure of Marion Walker from the Advisory Council on the Misuse of Drugs (ACMD) means that it no longer has a pharmacist representative on the board, contravening its statutory requirements, The Times has learnt.

Mr Johnson is to hold urgent talks with members of the ACMD, who wrote to him yesterday expressing “serious concerns” about the council’s relationship with Government.

It also emerged that the Home Office has started a review of the ACMD to look at whether it is accountable, if it is “discharging its functions” properly and if it continues to represent value for money. The review, which was launched last month and also covers the Animal Procedures Committee, is being conducted by Sir David Omand, a former permanent secretary.

The ACMD is responsible for reviewing all issues of drug misuse and advising Government on abuse, dependency and related social problems.

Under the Misuse of Drugs Act 1971, the Home Secretary is not permitted to amend the classification of any drug, including adding new ones to the list, “except after consultation with or on the recommendation of the advisory council”.

The law requires that six of council members represent particular fields, with Ms Walker the sole pharmacy specialist. Sir Leszek Borysiewicz, chief executive of the Medical Research Council, said that ministers risked losing the confidence of expert advisers across government unless they confirm their independence after the sacking. He said that the dismissal of the chief drugs adviser had created an “incredibly regrettable situation that has a potentially negative effect on the relationship between scientists and the Government”.

Sir Leszek, who heads a body that spent £704 million of public money on research in 2008-09, is the highest-ranking scientist on the government payroll to speak out so far over the Nutt affair.

Times Recommends

• How I lost the gift of joy for a while
• Why Ann Widdecombe has got it wrong
• Alas, it’s the end of the road for petrolheads