The UN strategy on drugs over the past decade has been a failure, a European commission report claimed yesterday on the eve of the international conference in Vienna that will set future policy for the next 10 years.

The report came amid growing dissent among delegates arriving at the meeting to finalise a UN declaration of intent.

Referring to the UN's existing strategy, the authors declared that they had found "no evidence that the global drug problem was reduced". They wrote: "Broadly speaking, the situation has improved a little in some of the richer countries while for others it worsened, and for some it worsened sharply and substantially, among them a few large developing or transitional countries."

The policy had merely shifted the problem geographically, they said. "Production and trafficking controls only redistributed activities. Enforcement against local markets failed in most countries."

Representatives from governments are split in their efforts to formulate an international drugs policy for the next decade. The UN Commission on Narcotic Drugs is due to formulate a strategy over the next two days, but there is widespread disagreement among delegates and a general feeling that an opportunity for a united approach has been lost.

In an article for the Guardian, Mike Trace, chairman of the International Drug Policy Consortium, says: "We're about to see the international community walk up the political and diplomatic path of least resistance. It will do nothing to help the millions of people around the world whose lives are destroyed by drug markets and drug use. And the depressing thing about it is that we can all book our seats for 2019, to go through this charade again."

Antonio Maria Costa, executive director of the UN Office on Drugs and Crime, has defended the approach. He is due to talk today on organised crime, which he has described as "one of the unintended consequences of drug control". He will warn that "a criminal market, of staggering proportion, risks undermining drug control" and outline a three-pronged approach to tackling drug-related crime.

In London, however, Lady Meacher, speaking on behalf of more than 30 members of the Lords, warned that the existing hardline prohibitionist strategy, which has been led by the US, had been deeply damaging. It was now being challenged by politicians, scientists and lawyers around the world, she said.

"We are concerned that the war on drugs has failed and the harm it has caused is far greater," said Meacher, at a briefing organised by the drugs advice charity Release. "What we want the UN to do is accept that the previous declaration was hopelessly unrealistic."

She said that Barack Obama had yet to appoint a new drugs tsar in the US but there were already signs that he was adopting a more liberal approach to the issue. The US president has lifted the ban on federal funding for needle exchange programmes, which are seen as crucial in the struggle to combat the spread of HIV.Kasia Malinowska-Sempruch, director of the global drug policy programme at the Open Society Institute, Warsaw, said: "It is now clear that after months of negotiations, millions of people around the world will continue to suffer needlessly. Thanks to the global 'war on drugs' over the past decade, close to 2 million people living in the former Soviet Union are infected with HIV, half a million US citizens languish in prison for non-violent, drug-related crimes, and billions of dollars are spent on destructive military actions in Colombia while the production of cocaine continues to rise."

The first two days of the session will be held at ministerial level to assess progress made in the decade since a special session of the UN general assembly set the target of a "drugs-free" world. The aim has been criticised for not addressing the problems of addiction and treatment.

Prof Tim Rhodes, of the London School of Hygiene and Tropical Health, said the number of injecting drug users around the world could have reached 15 million and this was responsible for 10% of global HIV infections.

Rhodes said the problem was particularly serious in Russia, where intensive street-level policing had exacerbated the difficulties.