Half of all police forces in England and Wales expect to spend less time tackling illicit drugs as a direct result of budget cuts, according to a survey by a drugs policy thinktank.

The UK Drug Policy Commission says that the areas most likely to suffer include the test purchasing of drugs, forensic testing and drug-related undercover surveillance operations – all of which will have a detrimental effect on operations to pursue higher-level drug importers and traffickers.

Yet, the survey shows that many forces are expecting to spend more time reclaiming and seizing assets from drug offenders, including the detection of drug money laundering and other activities which could raise income.

The results of the UKDPC's survey are being presented on Tuesday to the Association of Chief Police Officers' drugs conference. They are based on returns from 29 of the 43 police forces in England and Wales as well as 52 basic command units, representing 25% of all police commanders. One officer anonymously responded to the survey: "It's just a timebomb in society. If we don't continue to fight it we will gradually lose the battle."

The findings include:

• 58% of forces expect to reduce their spending on tackling illicit drug problems and 51% expect to reduce the time they spend on drug-related activities. A third of the forces that responded said they expected drug-related activities to fare worse than any other area of policing.

• 45% expect reduction in test purchasing; 44% expect reduction in forensic testing; 38% expect reduction in drug-related covert surveillance operations.

• Many forces also face reductions in local partnership work, with 38% expecting to do less drugs works with community groups, and a third expect less work with local authorities. Officers expressed concern that this could lead to knock-on effects as gaps were created that some might expect the police to fill. A third of forces said they were going to reduce the drugs education work they do with schools.

• Just over a quarter also reported that their use of drug dogs would be curtailed.

Police forces raised concerns not only over the potential impact of cuts on their ability to prosecute those involved in drug supply, but also their ability to identify and keep up to date with new drugs.

"Reducing capacity to access intelligence about drugs in their area [through test purchasing and forensic testing operations] could also diminish their capacity to fulfill anticipated new powers around the temporary banning of new substances," says the report.

The UKDPC survey cited one officer who noted that it was impossible to investigate the estimated 400 cannabis farms in his area without diverting resources from gun crime investigations or enforcement activities involving heroin and crack.

"We don't know what we're picking up intelligence-wise. And because of the implications for testing we're not emptying amnesty bins. We're not going looking for anything legal highs wise … I suspect if you took a straw poll of forces they wouldn't know what they've got," said another officer, referring to a reduction in testing as a result of a shakeup in the forensic science service.

Roger Howard, chief executive of the commission, who presented the survey results to the Acpo drugs conference, said: "It's never been possible to police everything and we shouldn't pretend otherwise. But what seems to be happening in response to the government's reduction in police resources is that cutting down on policing drug markets offers a path of least resistance. Drugs production and supply offences are often invisible: if you don't look for them, they don't register," said Howard.

"But officers are telling us that they're worried about the long-term consequences. They're saying that if you take your foot off the pedal on enforcement over drugs supply, you risk storing up much greater problems for the future."