A Wirral Euro MP who campaigns for the legalisation of cannabis has hit out at the decision by Home Secretary Alan Johnson to sack the government’s chief scientific advisor.

Chris Davies claimed that the dismissal of professor David Nutt, chairman of the Advisory Council on the Misuse of Drugs, proved that official policy was now based on prejudice not on fact.

The Liberal Democrat MEP, who stresses he has never taken an illegal drug but was convicted of cannabis possession in 2002 after taking part in a political protest against the law, accused the Home Secretary of trying to stifle dissent.

He said: “David Nutt’s offence was to do his job as a scientist and to point out that there is no basis for regarding cannabis or ecstasy as more dangerous than alcohol or tobacco.

“He is the equivalent of the boy who spoke up against public convention and said that the emperor was wearing no clothes.”

Mr Davies claims that the government’s refusal to follow the example of Belgium, the Netherlands, Switzerland and Portugal, where possession of small quantities of cannabis is not a criminal offence, pushes users of the drugs into the hands of heroin suppliers.

The MEP argues that the legal prohibition of drugs other than alcohol and tobacco has made criminals rich, and has provided money used to finance terrorist activities across the world.

He said: “If people could buy cannabis from a chemist, they wouldn’t need to buy it from a heroin dealer. "If Tesco supplied pot, the profits wouldn’t go to terrorists.”

He is calling for government policy to be based on a scientific assessment of the dangers from using all substances, and a clear separation between "soft" and "hard" drugs.

mr Davies added: “Instead of sacking people who tell the truth about drugs, the Home Secretary should be taking action to tackle the alcohol-fuelled violence that makes our towns and cities such dangerous places every Saturday night."