The row between the government and its drugs advisers escalated last night with the resignation of three more scientists.

Chemist Simon Campbell, psychologist John Marsden and scientific consultant Ian Ragan stepped down from the Advisory Council on the Misuse of Drugs (ACMD) following showdown talks with Home Secretary Alan Johnson.

The meeting was held amid the fallout from the sacking of the government's chief drugs adviser David Nutt over his controversial remarks about cannabis, Ecstasy and LSD.

A Home Office spokesman said: "Today's resignations were regrettable but discussions with the ACMD today were constructive."

Dr Campbell said last night he did not want to comment on his resignation until he had formally written to the Home Secretary.

He said it was "totally inappropriate" for details of today's ACMD meeting to be leaked.

Dr Campbell, a former president of the Royal Society of Chemistry, previously worked for Pfizer and was part of the research teams that discovered Viagra.

The synthetic organic chemist serves on various scientific bodies and was appointed CBE in 2006 for services to science.

Dr Marsden is a research psychologist and senior lecturer in addictive behaviour based at the Institute of Psychiatry, while Ian Ragan is director of CIR Consultancy Ltd, which provides services to the pharmaceutical and biotech industries.

The sacking of Prof. Nutt more than a week ago prompted a wave of protest from the scientific community.

Two other members - Marion Walker and Dr Les King - quit in protest and Prof. Nutt warned that his former colleagues could resign en masse at today's meeting because of disquiet at the treatment of their chairman.

Science Minister Lord Drayson acknowledged earlier this week that there was "serious concern" among the scientists.

Prof. Nutt, who was barred from the meeting, said last night he had spoken to each of the resigning advisers and attributed their decision to quit to a refusal by ministers to respect scientific principles.