Johnson to ban sale of the legal high mephedrone

The Home Secretary is expected to announce a ban on the "legal high" mephedrone later today, although experts warn that could drive the trade into the hands of criminal dealers.

Alan Johnson's decision to outlaw mephedrone, which is available openly over the internet and in alternative lifestyle shops as a plant food, will follow an all-day meeting of the Advisory Council on the Misuse of Drugs.

The Government has already indicated that it will act immediately on the recommendation it receives from the council – most likely designating it a Category B drug beside cannabis and speed and making it subject to up to 14 years in prison for dealing offences.

The legislation is expected to be hurried through Parliament before it rises for the general election campaign.

But while there has been a growing clamour to ban the drug after it was linked to four deaths in a few months, fears mount that little is known about what will happen when it is outlawed. It is expected to rise in price from its current £10 a gram, while shortfalls in supply will lead to the drug being bulked out with adulterants. The pattern of recent years has seen drugs such as cocaine and ecstasy decrease in purity while falling in price.

Experts have been shocked by the rate at which use of mephedrone has spread. It was little heard of outside the club scene until late last year but since then police have warned that it has reached almost every community in the UK. The sudden growth in its popularity followed the long-awaited banning of two other legal highs, GHB (gammahydroxybutrate, better known as "liquid ecstasy") and GBL (gammabutyrolactone) in December.

It is feared that dealers and users are stockpiling mephedrone ahead of the ban. The subject was being discussed on internet forums dedicated to the substance yesterday with some users, who continue to prize it for its speed-like high, claiming to have bought up to 20g at a time to tide them over until new supply routes emerge.

Some of the biggest mephedrone websites were offering "Easter special" deals on the drug, giving away two grams free with orders over £100.

Martin Barnes, the chief executive of the charity Drugscope, a leading independent centre on advice about drugs, said it presented a completely new challenge for policy makers. "With mephedrone we are in a quite exceptional situation," he warned. "It would be naive to believe that controlling it is going to stop its supply and use. For some people, it will be a deterrent but for some users it won't," he said.

Though he described a ban as a "pretty blunt instrument" he said there was "anxiety" that it should not be on sale when the summer festival season begins, tempting young people into experimenting with it for the first time. One concern is that taking it in hot weather could increase the tendency of users to overheat and thus lead to more deaths. Other side-effects include insomnia, heart palpitations and blue limbs.

As yet, however, there have not been full coroners' inquests into any of the deaths linked to mephedrone. But while there were no clinical studies available, and the drug has not formed part of the reporting for the British Crime Survey until now, evidence from hospital accident and emergency departments suggests that enough users were falling ill after taking it to suggest it was a danger to public health, Mr Barnes said.

The drug is often taken in a cocktail of other substances including ecstasy, amphetamines and alcohol and because the high is relatively short-lived, users are tempted to binge, snorting or swallowing several grams over extended periods. Professor David Nutt, who was sacked as chairman of the ACMD, urged the Government last week not to ban the substance until there was a full body of evidence. He suggested allowing adults to take the drug under close supervision rather than driving it underground.

At present the drug is produced in China and imported openly to Britain where, provided it is sold with a legal disclaimer that it is not for human consumption, dealers are able to bypass laws governing food and medicine as well as the Trade Descriptions Act.

Banned substances: A history

*1916 Concern about drug use by troops during the First World War resulted in a ban on cocaine and opium.

*1928 "Indian hemp and all resins and preparations thereon" made illegal in the UK following signing of the Geneva International Convention on Narcotics Control by the League of Nations.

*1955 UK bans heroin import, export and manufacture despite a campaign by The Times, which argued there were only 317 drug addicts in Britain, a fraction of whom were addicted to heroin.

*1956 Sale of over-the-counter amphetamines, "pep pills", outlawed.

*1966 LSD banned.

*1977 Ecstasy (MDMA) banned. First discovered by German chemists in 1912 for use in chemical warfare, but only widely available in the late 1980s.

*2005 Mushrooms or any fungus containing psilocin categorised as Class A.