General Barry McCaffrey was confronted by placard-waving protesters when he launched ResourceNet, a drugs education and information internet site, at Goldsmith's College in London.

Transform, one of the protest groups, said it was worried the presence of General McCaffrey, known for his hardline stance, meant the hardening of the UK's drug policy.

General Barry McCaffrey says cannabis leads to stronger drugs

The general, whose opposition to policies such as needle exchange programmes has angered many drug experts in the US, is touring addiction projects in London.

He is also meeting Home Office minister Paul Boateng and cabinet co-ordinator Mo Mowlam, whose remit includes responsibility for drug policy.

General Barry McCaffrey: "Drugs are a cancer which young people must be protected from"

Mr Hellawell said the general was in London to learn "not preach" and added that the international community needed to take a common stand to tackle drug trafficking.

He said: "It is an international problem that needs an international response."

General McCaffrey, a former Gulf war commander, was appointed director of the US Office of National Drug Control Policy and is the inspiration for the creation of Mr Hellawell's post in 1996.

He said he was "delighted" to be able to work with his British counterparts and was particularly interested in reducing drug use in sport.

MP says US is wrong

However, Labour MP Paul Flynn, who recently failed in his attempt to have cannabis legalised for medicinal use, said the UK should not listen to the general's tough line on drugs.

Paul Flynn: "The US has got its drug policy wrong"

"Asking the American drugs czar for advice about our drugs policy is about as useful as asking Pinochet or the president of China for advice about our human rights policy," he told the BBC.

"America has the worst drugs problem in all the world and they are getting worse as far as heroin is concerned, although they have had some reduction in cannabis.

"The lesson is that prohibition increases all drugs problems, but regulated decriminalisation reduces all drugs problems."

Drugs 'a cancer'

The general said that illegal drugs were a "cancer" within society.

He is known for his consistent opposition to the use of needle exchange schemes.

Paul Flynn, Labour MP: "The US has the worst drug problem in the world"

Last year he called the programmes "magnets for all social ills", including drug dealing and prostitution.

He has also refused to accept, to the frustration of some patients' groups, any medical benefits of marijuana and is against considering cannabis differently to hard drugs like heroin.

"The most dangerous drug in America is a 12-year-old smoking pot and abusing alcohol," he said.

"If you can get a young person between the age of about nine and 18 where you minimise their exposure to drug-taking behaviour we find they will never have, statistically, a compulsive drug-use problem their entire life."

Sixteen months ago General McCaffrey slammed the Dutch government's liberal drugs approach by saying the country, as a result, had a murder rate twice that of the US.

The actual figure is one quarter of the American one.

The general said education and prevention were "the heart and soul" of reducing drug use.

He said drug use in the US had fallen by 50% over the past 20 years, with just 6% of the population currently taking drugs compared with 14% in the late 1970s.

Cocaine use, meanwhile, had fallen 70% between the 1970s and 1990s.

But he admitted that the US still had some 810,000 heroin users.