Cannabis upgrade 'very damaging'

Cannabis was downgraded to class C under Tony Blair

A group of leading scientists and MPs has attacked plans to reclassify cannabis as a more dangerous drug.

In a letter to the Guardian newspaper, the signatories say it would be "very damaging" for the government to ignore expert advice not to upgrade the drug.

The home secretary wants to change it from class C to class B, putting it on a par with amphetamines, such as speed.

The letter says this would risk reversing the downward trend in the use of cannabis since 2004.

It also says it would send confusing messages to the public about the more serious dangers of class B drugs.

'Schizophrenia'

Cannabis was downgraded to class C in 2004, but since then there has been growing concern about the potential impact on mental health, particularly of stronger "skunk" varieties.

Despite these fears, in May, the Advisory Council on the Misuse of Drugs (ACMD) concluded in a government-commissioned review that it should stay as class C.

The council said cannabis was not as dangerous as other class B substances and evidence suggested only a "probable, but weak, causal link between psychotic illness, including schizophrenia, and cannabis use".

Home Secretary Jacqui Smith wants to overrule that recommendation, a move which will be debated in the House of Lords on Tuesday.

The classification system must be credible Letter from leading scientists and MPs to the Guardian newspaper

The letter, whose signatories include two former chief scientists, Sir David King and Lord May, said that in pressing ahead with reclassification, "the government has rejected the explicit advice of its appointed experts... for the first time in nearly 30 years".

"The impact of Parliament agreeing to the government's policy could be very damaging," it said.

"Cannabis use has fallen in recent years, especially following its downgrading to class C in 2004, and it is obviously unwise to risk reversing that trend.

"The classification system must be credible - reclassification would send out an ambiguous message about the dangers of current class B drugs.

"Even more importantly, the move would be a sad departure from the welcome trend... of public policy following expert scientific advice unless there is new evidence."

Drugs education

The letter said the ACMD had examined "all the available and latest evidence on short and long-term health risks, as well as social harms, public attitudes and policing priorities".

It said experts had recommended better drugs education and a crackdown on dealers, but concluded that it would be wrong to make possession of cannabis a more serious criminal offence.

The letter urged peers to vote in favour of an amendment deferring any decision on reclassification until at least 2010.

Also among the signatories are Professor Colin Blakemore, former head of the Medical Research Council; Dr Evan Harris MP, Lib Dem science spokesman; and Sir Gabriel Horn, chair of the Academy of Medical Science's working group on brain science, addiction and drugs.