Two thirds of the $1.7 billion Australian state, territory and federal governments spent on drugs went on law enforcement, according to the Government Drug Policy Expenditure in Australia report to be released on Thursday.

Drug experts say Australia's spending simply does not match the evidence and have called for a drastic readjustment in favour of treatment and harm reduction.

Report author Alison Ritter said it was gravely concerning that spending on harm reduction measures had dropped since a similar analysis in 2002.

"It's a shift in policy that hasn't been formally acknowledged," she said. "There is absolutely no reason that investment should have decreased."

The report found Australia spent 2.1 per cent of its drugs budget, or $36 million, on harm reduction in the 2009-10 financial year. This compared with $361 million, or 21 per cent, on treatment and $1.1 billion on law enforcement.

Professor Ritter, the director of the drug policy modelling program at the University of NSW, said it was difficult to study the effects of law enforcement, so it was hard to compare it to treatment and harm reduction.

"We don't have good evidence that law enforcement works, and we have anecdotal evidence I suppose that it might not work as a policy," she said.

"We continue to arrest people and drugs keep coming into Australia … and profits continue to be made."

Australian National Council on Drugs executive director Gino Vumbaca said politicians were under pressure to put money into law enforcement.

"It is easy to show off your interception of half a ton of drugs, but it's much harder to show how a service has improved the lives of 20 people over a year," he said.

John Ryan, the chief executive of drug harm minimisation group Anex, called for a productivity commission investigation into Australia's drug spending.

"Australia is meant to have an evidence-based drug policy, yet investment in proven economically and socially efficient harm reduction programs has fallen away as Australia's illicit drug markets have morphed and grown," he said.

"Some serious number crunching and examination of evidence, rather than purely emotional or ideological reactions, is required.''