Tough action by police and customs on drug seizures is failing to curb demand or supply at street level, new research suggests.

The UK Drug Policy Commission report found the £5.3 billion drugs market was proving “extremely resilient” to crackdowns by law enforcement agencies, despite hundreds of millions of pounds spent each year on tackling the problem.

It claims even significant drug seizures and high-profile convictions of traffickers and dealers usually fail to have an impact on supply and demand due to the scale of the market.

Dealers are able to adapt quickly to disruptions by reducing the purity of batches, the report added.

The number of Class A drug seizures in England and Wales more than doubled between 1996 and 2005, according to the report.

But an estimated 60% to 80% of drugs would need to be seized regularly to put major traffickers out of business, even though seizure rates on this scale have never been achieved in the UK or elsewhere.

Tim McSweeney, one of the report authors, said: “Within the research literature there is a consistent call for a better understanding of how drug markets operate and the role that enforcement can have in reducing the damage caused by them.

“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 and represents value for money.”

The report calls for more to be done to reduce the effect of drugs on communities, for instance, by tackling drugs-related “collateral damage” such as gang violence and prostitution.

The authors argue this would have a greater impact on the drugs trade than big hauls.

David Blakey CBE QPM, of the UK Drug Policy Commission, said: “Drug dealers must be brought to justice, but we should recognise and encourage the wider role that the police and other law enforcement officials can play in reducing the impact of drug markets on our communities.”