Three more government drug advisers resign over the home secretary's sacking of Professor David Nutt as chairman of the Advisory Council on the Misuse of Drugs (ACMD).

The three all resigned after a face-to-face meeting with Alan Johnson, the home secretary, which was called in an attempt to heal the rift between the scientists and the government over Nutt's sacking.

The loss of three more members of the council brings the total who have gone to six out of an original membership of 31 the home secretary appointed to advise him on drugs policy. Many of those remaining, who include police officers and judges, are there as representatives of organisations and are unlikely to tender personal resignations.

The three further resignations came from across industry and academia. Ian Ragan was appointed to the ACMD in February last year, and is director of a consultancy for the pharmaceutical and biotech industries, CIR Consultancy Ltd.

John Marsden, a research psychologist at the Institute of Psychiatry, was appointed to the committee in January last year. And Simon Campbell, a member of the committee since April 2008, is a synthetic organic chemist and former head of Worldwide Discovery and Medicinals R&D Europe at Pfizer. He also sits on various scientific bodies including the Cancer Research UK discovery co-ordinating committee, and is a fellow of the Royal Society.

The three are believed to have argued for Nutt's reinstatement.

The Liberal Democrat science spokesman, Evan Harris, 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."

A joint statement from the Home Office and the ACMD, issued after the meeting, said that the talks had been "very constructive", but it stressed that discussions were "continuing" between the department, the government's chief scientific advisors and the drug advisers about how they could work together in future.

The scientists in particular wanted assurances their reports and recommendations would in future be taken seriously, and sought an agreement over how their advice was handled by ministers.

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

Nutt, a pharmacologist at Bristol University and Imperial College London, was sacked last month after criticising the government's decision to upgrade the legal classification of cannabis, arguing that it was less harmful than alcohol and cigarettes.

Johnson said that Nutt had "crossed a line" into politics with remarks that amounted to "lobbying against government policy".

Dr Les King, the former head of the drugs intelligence unit of the Forensic Science Service, and Marion Walker, the clinical director of Berkshire Healthcare NHS foundation trust's substance misuse service, resigned in the immediate aftermath of Nutt's sacking.

A letter sent by the ACMD before the meeting to the home secretary said it was clear that a majority of its members had serious concerns about the role and treatment of the council and its work as a result of Nutt's dismissal: "For some members, these matters are of such seriousness as to raise the question whether they can, in good conscience, continue on the Council."