The fall-out over the departure of David Nutt, the Government's top drugs adviser who is based at Bristol University, continued yesterday with the resignation of a prominent member of the government's drugs advisory panel.

Leading scientist and broadcaster Lord Robert Winston also said he was "disappointed" about the treatment of Professor Nutt, claiming it showed a lack of scientific understanding.

Prof Nutt heads up the Psychopharmacology Unit at Bristol University. He was forced to resign on Friday in the wake of the row over the dangers of class A drugs.

Home Secretary Alan Johnson asked Prof Nutt to resign as chairman of the Advisory Council on the Misuse of Drugs, saying he had "lost confidence" in his ability to give impartial advice.

Yesterday, Dr Les King, who worked for the Forensic Science Service (FSS) for 30 years, and has been associated with the drugs advisory panel for 15 years, said Mr 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 yesterday.

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."

Labour peer Lord Winston warned that the Government would be ignored if it gave advice to the public that did not take account of scientists' opinions and said Prof Nutt had made a "very reasonable" point about the relative dangers of illegal and legal drugs.

He told BBC Radio 4's The World This Weekend he was "very surprised and disappointed" by Mr Johnson's actions.