Three members of the Government’s drugs advisory panel resigned last night after Alan Johnson failed to persuade them to stay on after his sacking of David Nutt as the body’s chairman.

A source close to the Advisory Council on the Misuse of Drugs (ACMD) named the three advisers as Simon Campbell, Dr Ian Ragan and John Marsden.

Two other members of the committee, Les King and Marion Walker, resigned last weekend in protest at the Home Secretary’s dismissal of Professor Nutt for questioning government policy on the classification of Ecstasy and cannabis.

The latest resignations come as a blow to the Home Secretary, who had hoped to prevent further departures from the council by meeting its remaining 28 members this afternoon to discuss their concerns.

While the majority of the ACMD issued a joint statement with Mr Johnson describing their discussions as “very constructive”, three were unconvinced by his assurances about the council’s continued independence and decided to resign.

The statement said: “The Home Secretary emphasised the value he placed on ACMD’s advice, the important contribution the ACMD had made to government drugs policy in the past and how he expected it to continue do so in the future. The ACMD summarised their concerns regarding how their advice is received by the Home Office and over the dismissal of Professor Nutt.

“The discussions were very constructive and it was agreed that the ACMD would continue discussions with the Home Office and Government Chief Scientific Advisors in establishing a way to work collaboratively together into the future with the common purpose of reducing drug-related harms in the UK.”

Mr Johnson said that a statement of principles on the independence of government science advice, proposed by more than 50 senior scientists, was being considered by the Prime Minister and the Government’s Chief Scientific Adviser, Professor John Beddington.

Lord Drayson, the Science and Innovation Minister, told The Times last week that the Government would accept the principles, though certain details have still to be agreed.

A Home Office spokesman said that it woud provide further details “in the near future” of how the department and council will work together in future and how advice from the council is considered by ministers.

The Times understands that the ACMD did not ask Mr Johnson to apologise for sacking Professor Nutt at the meeting, and that the Home Secretary gave assurances about meeting the council before rejecting its advice in future. Professor Beddington also met the council to discuss their concerns over the continued independence of their scientific advice.

An ACMD insider told The Times that the three members to quit were Dr Campbell, a former head of worldwide discovery at the drugs company Pfizer and a former President of the Royal Society of Chemistry; Dr Marsden, a research psychologist at the Institute of Psychiatry; and Mr Ragan, a pharmaceutical and biotechnology industry consultant. None of the three was available for comment.

The departures of Dr Campbell and Dr Ragan would be particularly damaging as this would leave the council without representation from the pharmaceutical industry, which is required by law. Professor Walker’s resignation had already left the council without a pharmacist, another required discipline.

Professor Nutt said: “I’m not surprised. The way I have been treated was reprehensible, and I’m pleased to have the support of these other council members.”

Evan Harris, the Liberal Democrat science spokesman, said: “The latest resignations represent a deepening in the crisis of confidence of scientists in the Government — in particular, in the Home Secretary. That they come after Alan Johnson met the ACMD demonstrates that he just doesn’t get it when it comes to the importance of respecting the academic freedom and integrity of independent, unpaid, science advisers.

“Ministers are entitled to their own opinions, but not to their own facts. The cost of the failure of the Home Secretary to understand the lessons of the BSE Inquiry will be poor policy — unless the Prime Minister acts decisively to bring the Home Office and rest of Government into line with established good practice.

“By clumsily and unfairly sacking David Nutt, Alan Johnson has been rewarded with five resignations in protest. That takes a certain kind of ineptitude.”

Last night the Home Office said the resignations were regrettable but talks with the ACMD were constructive.

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