Home Secretary Alan Johnson has defended the sacking of chief drug adviser Professor David Nutt

Members of the Government's drug advisory body questioned its future in the wake of the sacking of Professor David Nutt, and demanded showdown talks with Home Secretary Alan Johnson.

Scientists on the Advisory Council on the Misuse of Drugs (ACMD) threatened to quit unless Mr Johnson addressed "serious concerns" about the council's relationship with Government.

In a letter they called for "clarity and assurances" from ministers about how they viewed the ACMD and how they would treat its advice in future.

Details of the letter emerged as Mr Johnson escalated his criticism of Prof Nutt, accusing him of breaching the official code of conduct for advisers. Prof Nutt had failed to give the Home Office advance warning of last week's paper in which he said alcohol and tobacco were more dangerous than Ecstasy and LSD, and questioned the decision to downgrade cannabis, Mr Johnson said.

It also emerged the Home Office has ordered 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. Mr Johnson, who was called to the Commons to answer an emergency question from the Tories, denied the review - which was announced two weeks ago - was linked to the row over Prof Nutt's dismissal.

While praising the work of the ACMD as "invaluable", and agreeing to meet its remaining members in person, he stated again he had "lost confidence" in Prof Nutt last week. The job of the council's chairman whose job was to "advise rather than criticise Government policy", he said. He said: "The role of such advisers is to provide independent advice to government based on their professional scientific expertise. The role of government is to consider that advice carefully, along with all other relevant factors, and for this House to endorse or reject those decisions, where appropriate."

Prof Nutt had acted "without prior notification to my department, to initiate a debate on drugs policy in the national media ... and accusing my predecessor of distorting and devaluing scientific research".

The meeting could take place next week, when council members convene in London for a pre-arranged meeting. In their letter to Mr Johnson, signed by a majority of ACMD members, they said: "The removal of Professor Nutt has brought to the fore wider and pre-existing concerns amongst members about the role and treatment of the council and its work.

"For some members these matters are of such seriousness as to raise the question whether they can, in good conscience, continue on the council," they say in the letter. "In this situation members wish for clarity and assurances about how the ministers view the council's advice and will view the council's advice in the future."