Britain's antiquated drugs laws stand accused of failing millions of people because they bear little or no relationship to the harm caused by everything from a hit of heroin to a seemingly harmless pint of lager.
The Home Office has been warned by its own senior advisers that alcohol and tobacco are more harmful to the nation's health than the Class A drugs LSD and ecstasy.
Research by medical experts, who analysed 20 substances for their addictive qualities, social harm and physical damage, produced strikingly different results from the Government's drug classification system.
Heroin and cocaine, both Class A drugs, topped the league table of harm, but alcohol was ranked fifth, ahead of prescription tranquillisers and amphetamines.
Tobacco was placed ninth, ahead of cannabis, which has recently been downgraded from a Class B to Class C drug, at 11th.
Alcohol and tobacco, and solvents, which can also be bought legally, were judged more damaging than LSD (14th) and ecstasy (18th).
The warning on alcohol comes amid growing alarm among ministers over a surge of "binge drinking" over the last decade. They fear it is fuelling rising levels of violent crime and creating long-term health problems for the nation.
Methadone, used to wean heroin addicts off the drug, also scored highly, being judged more dangerous other Class A substances.
The research will put more pressure on the Home Office to a rethink the 35-year-old system for classifying illegal drugs as Class A, B or C substances. It reflects the penalties for possessing them or dealing in them, but that means heroin is categorised alongside drugs such as ecstasy.
The analysis was carried out by David Nutt, a senior member of the Advisory Council on the Misuse of Drugs, and Colin Blakemore, the chief executive of the Medical Research Council. Copies of the report have been submitted to the Home Office, which has failed to act on the conclusions.
Professor Blakemore told the BBC Radio 4 Today programme: "Alcohol, on our classification, is the fifth most harmful drug - more harmful than LSD and by a long way than ecstasy and cannabis and a whole range of illegal drugs.
"That's not to say there's any argument that alcohol should be made illegal, but it does give one a feel for the relative harm potential from any drug."
Strongly influenced by the research, MPs on the Commons science and technology select committee demanded an overhaul of the system to give the public a "better sense of the relative harms involved".
They called for a new scale to be introduced, rating substances on the basis of health and social risks and not linked to legality or potential punishments.
They questioned whether ecstasy and magic mushrooms should remain in Class A and called on the Government's drug adviser, the Advisory Council on the Misuse of Drugs (ACMD), to look at the issue.
Phil Willis, who chairs the committee, said the current classifications were "riddled with anomalies" and were "clearly not fit for purpose".
"This research shows why we need a radical overhaul of the current law and a radical review of the classification system," he said.
"It's clearly not fit for purpose in the 21st century, neither for informing drug-users or providing public information."
One committee member, the Liberal Democrat MP Evan Harris, said that putting drugs in the wrong category "undermined the whole system". "Lots of young people know that there's a difference between ecstasy and heroin," he said.
Martin Barnes, chief executive of the drugs charity DrugScope, said: "With ecstasy, although it is a harmful substance and has led to deaths, if you look at its harmfulness with other Class A drugs, it is much less harmful in terms of links to criminality, mortality and poor health.
"But one of the difficulties, if the classification of a drug is changed, is that that then becomes a key issue in terms of politically how it is received."
Cannabis was reclassified from Class B to Class C in 2004 on the advice of the ACMD. The move prompted fierce criticism in some quarters and was later reassessed in light of new scientific data.
Critics said the change sent out a message that cannabis was not harmful, and downgrading it had caused confusion over whether the drug was still banned.
But in January, the then Home Secretary Charles Clarke announced that after an ACMD review of evidence, the decision to downgrade cannabis would stand. His successor, John Reid, has so far made no pronouncements on drugs policy.
Lord Victor Adebowale, chief executive of the social care organisation Turning Point, said: "Our work across the country with people affected by drugs and alcohol tells us that a classification system should take into account the health, social and economic costs of substance misuse."
Reforming the laws
By Jeremy Laurance
More than a third of people claim to have taken illegal drugs during their lifetime, and 10 per cent say they have done so in the last year. Efforts to restrict drug use have failed to curb high rates of consumption in the UK. Though use of heroin and crack cocaine is comparable to other countries, use of recreational drugs is higher.
Britain had a relatively liberal approach to drugs in the 1960s, with heroin prescribed to addicts. The 1971 Misuse of Drugs Act introduced "ABC" classification: Class A drugs such as heroin carry the highest penalties, with lesser penalties for class B and C drugs.
But evidence has shown policies based on enforcement alone have failed. In 2002, the Home Affairs Select Committee, which included the future Tory leader, David Cameron, said this was the "single lesson" that had come from the previous 30 years. It backed a proposal by David Blunkett, former Home Secretary, to downgrade cannabis to class C.
A trial relaxation of the laws on cannabis went ahead in Lambeth, south London, where police guidance was changed from arresting and charging people for possession of small amounts of cannabis, to focusing on dealers. The experiment was extended nationwide with the reclassification of cannabis in 2004. The Government is now considering a proposal for a new lower threshold for a presumption of supply, which sources suggest could be 5g of cannabis and 5 tablets of ecstasy. The proposal has been criticised by the Advisory Council on the Misuse of Drugs as a retrograde step that will lead to more police time being spent on users rather than dealers.
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