The findings indicate a far higher use of drugs among criminals than was suggested at the weekend when government sources leaked the fact that one in five of those tested in the survey had been using heroin.
Home Office sources said yesterday that the selective leaking was an indication of the government's determination to draw the line between hard and soft drugs.
Although Labour is opposed to the decriminalisation of cannabis, the high level of soft drugs use among those arrested was being deliberately played down because of the lack of evidence linking it to acquisitive crime, they said.
The leaking was intended to trail the announcement by Jack Straw, the Home Secretary, of proposals for drugs testing and compulsory treatment for criminal offenders. Mr Straw will outline his plans in an address to the Police Federation tomorrow.
A Home Office source said at the weekend: "There is very good evidence that these people who test positive for hard drugs are involved in quite extraordinary amounts of acquisitive crime, burgling and robbing their way around town to fund their habits."
The heroin revelation coincided with the news that Labour was appointing a "drugs tsar" to lead a campaign against abuse and the illegal trade in drugs.
But no reference was made to the finding in the survey that in addition to the heroin users, 50 per cent of people arrested had tested positive for other drugs, mainly cannabis, after agreeing to give urine tests in police stations.
The findings, which are preliminary and will not be published until later this year, have been made by a team co-ordinated by Dr Trevor Bennett of the Institute of Criminology at Cambridge University. Testing has been carried out in Cambridge, Manchester, London and Nottingham.
Harry Fletcher, assistant general secretary to the National Association of Probation Officers, said it was important to distinguish between casual drug users and those with a dependency.
"Our research shows that 25 per cent of those who come into contact with the police have a chronic drugs dependency and those are the ones that require treatment," he said.Reuse content