Mr McCaffrey, in the Netherlands on a fact-finding mission, criticised the high level of amphetamine and ecstasy production, much of which goes to the United States and Britain.

Holland's health minister, Els Borst, in turn said he refused to accept facts on the results of Dutch drugs policy.

She said the US's oppressive policy on drugs did not stop young people from experimenting.

Barry McCaffery points the finger at Dutch liberalism

Ms Borst, who had dinner with Mr McCaffrey on Thursday night, said: "When I say we prefer they only experiment with cannabis, he just falls silent and gazes ahead."

Mr McCaffrey, a former US Army General and Vietnam veteran, tried to play down his differences with the Dutch authorities, saying he was satisfied with his "very intensive and useful visit."

He said he had an "open and courteous exchange of views" with his hosts.

His views were made clear at a press conference when he pointed out that the Netherlands produces half of Europe's amphetamines and much of its MDMA (ecstasy).

Earlier he visited a methadone treatment project in Amsterdam.

Washington and The Hague do not see eye-to-eye on the latter's controversial new heroin maintenance programme, which provides registered addicts with good quality heroin.

The idea is to hit the pushers in the pocket and reduce the health risks from impurities.

Mr McCaffrey said: "It is our own view that this does not constitute good treatment, but instead ends up in essence leaving and marginalising an element of the population."

He also criticised Holland's coffee shop culture, whereby cannabis and marijuana are freely on sale in major cities such as Amsterdam.

Dutch opposition MP Wim von der Kamp thinks the visit has damaged relations

Dutch law permits possession of up to five grams (0.175oz) of soft drugs for personal consumption.

The US Government view cannabis as a "significant threat to drug dependency particularly among young people."

Mr McCaffrey admitted: "We do not have a common agreement on drug policy."

But he added: "It is not my purpose to persuade the Dutch authorities."

On Tuesday, even before he arrived, there was a row when US officials said Mr McCaffrey would warn Dutch authorities they were "putting American children at risk" with their relaxed laws on marijuana.

The Dutch health ministry reacted angrily and doubted whether his visit would "have any purpose".

A spokesman said he should "get his ideas more in tune with reality".

Mr McCaffrey's office later retracted the comments but many felt the damage was done.