Police are fighting a losing battle against drugs crime, with seizures having little impact on reducing supply or demand, research has suggested.
The UK Drug Policy Commission said despite the large sums of money spent tackling the problem, traditional police tactics were not working.
It said the £5.3bn British drugs market was too "fluid" for law enforcement agencies to cut supply. It added more should be done to reduce the effects of drugs oncommunities.
A Home Office spokesperson said: "The government agrees that enforcement in isolation is not effective."BBC home editor Mark Easton said the report was a "very bleak assessment of where we are in what some people call the war on drugs".
The report, titled Tackling Drug Networks and Distribution Networks in the UK, concluded that although the amount of Class A drugs seized between 1996 and 2005 doubled, the market had proved to be "extremely resilient".
This was despite 12% of the heroin and 9% of the cocaine in Britain being impounded during the same period, and despite the convictions of dealers and traffickers. The independent think-tank said dealers were able to adapt quickly to interruptions in supply, for instance by reducing purity, enabling them to maintain their profit margins. The report estimated that between 60% and 80% of drugs would need to be seized to put major traffickers out of business - yet crackdowns on such a scale have never been achieved in the UK.
It went so far as to warn that police crackdowns could have a negative effect on the problem.
They could threaten public safety and health by "altering the drug users' behaviour and potentially…setting up violent drug gang conflicts as police move dealers from one area to another", said our correspondent.
Instead, the study's authors suggested the government concentrated on the "collateral damage" of the trade - sex markets, gangs, human trafficking, corruption, drug-related crime and anti-social behaviour. They added that resources should be focused on disrupting "street-level markets" and tackling violence and intimidation in communities.
The criminal justice costs of class A drugs alone are estimated at £4bn ayear. Tim McSweeney, one of the report's authors, said: "We were struck by just how little evidence there is to show that the hundreds of millions of pounds spent on UK enforcement each year has made a sustainable impact."
David Blakey, of the UK Drug Policy Commission, said enforcement agencies tended to be judged by the amount they had managed to capture."This is a pity as it is very difficult to show that increasing drug seizures actually leads to less drug-related harm," he added.
The Home Office said seizures were only part of the government's approach,with intervention programmes getting 1,000 offenders into drug treatment each week."Many of the report's recommendations are already being implemented," the spokesperson added. "Our drugs strategy encompasses enforcement, prevention, education and treatment."
Our correspondent said while few politicians would suggest that less should be spent on being tough on drugs, the government's own 10-year drugs strategy was already cautious in its claims on the effectiveness of law enforcement."
There is a recognition that we "have to do more than just catch people and lock them up, we have to do something else, it's not working," he added.