A prominent member of the Government's drugs advisory panel has resigned in protest over the treatment of the committee's chairman Professor David Nutt.
Dr Les King said Home Secretary Alan Johnson had denied Prof Nutt his right to free speech when he called for his resignation.
Mr Johnson said he had "lost confidence" in Prof Nutt's ability to give impartial advice after the chairman of the Home Office's Advisory Council on the Misuse of Drugs criticised the Government.
"He (Prof Nutt) may be an advisor but he's still got the right to say what he likes. That was being denied," Dr King said.
The row which forced Prof Nutt's resignation was due to comments he made that ecstasy and LSD were less harmful than alcohol and cigarettes. He also criticised the decision to upgrade cannabis to class B.
Dr King, who worked for the Forensic Science Service (FSS) for 30 years, has been associated with the drugs advisory panel for 15 years.
He was head of the Drugs Intelligence Unit for 10 years before his retirement from FSS in 2001, when he became a co-opted member of the Home Office advisory panel.
Dr King, who became a full member last year, said the Government's attitude to the panel has been shifting in recent years and home secretaries now had a "pre-defined political agenda" when they asked for its expert advice.
"It's being asked to rubber stamp a pre-determined position," he said.
"If sufficient members do resign, the committee will no longer be able to operate."
