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 today.
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."
Dr King said he believes the panel needs to become "free from Government interference" in the same way as the National Institute for Clinical Excellence (Nice), the organisation which advises on medicines and clinical practice.
"I don't see why drugs can't be done the same.
"It can be totally depoliticised.
"It's all about harm. It's a scientific issue," he said.
Dr King emailed his resignation to the Home Office yesterday.
A Home Office spokeswoman today confirmed that it had been received.
"We can confirm that Dr Les King has resigned. We are not going to give a running commentary on the speculation around further resignations," she said.
"We will not be commenting further."
Dr King said the Government had "a right" to reject the panel's advice but he added that the attitude towards the panel had changed "very recently".
"I suppose it goes back to 2002 with (then home secretary) David Blunkett who was minded to reclassify cannabis downwards.
"He made it clear to us his wishes. The council supported that.
"In that situation it was something that the council readily agreed to. That wasn't too worrisome but that precedent then continued."Reuse content