A district court judge says the "very large" hole in addiction treatments is a major cause in high reoffending rates, putting a strain on prisons, society and families.

Judge John Walker says alcohol or drugs contribute to 80 per cent of cases before district courts and are rarely absent in serious violent offending cases.

But he said there was a very large hole in resources to treat addictions, often leading to untreated offenders slipping back into substance-abuse only to reoffend again and end up back in prison.

"There would hardly be a case, particularly involving violence, that comes before the court that does not have alcohol as a factor."

It costs $91,000 a year to house a sentenced prisoner. Research by the National Committee for Addiction Treatment shows that every $1 invested in treating addictions yields a $4 to $7 return, much of it in the reduction in substance-fuelled crime.

"It's not rocket science," Judge Walker said.

"It's a lot cheaper to treat, and I think there is a groundswell in that direction.

"Every time I get confronted by addictions that need treatment, the very next question is where, and how?

"We are constantly battling that and it is often unanswered."

Alcohol and drug counsellor Roger Brooking said 50 of the 51 prisoners he assessed in the past few years needed treatment.

Among his reports are two offenders who waited 24 years before being given an alcohol or other drugs assessment, and another who was not assessed until 12 years after his first conviction.

The cases involve repeat offenders whose list of offences include dangerous driving, possession of drugs, assault and murder.

Recidivism rates have changed little in the past five years. Nearly half (48 per cent) of released prisoners re-offend within a year, and 37 per cent end up back in prison within two years.

Official estimates say between 65and 90 per cent of prisoners have alcohol or drug problems.

The Government has identified alcohol as one of its four priority areas in its study examination of crime causes, including improving the availability and accessibility of treatment services.

The Law Commission will report to the Government this month on the reform of liquor laws, and alcohol and drug treatment in prisons is being doubled from 500 to 1000 placements.

Associate Health Minister Peter Dunne was concerned some district health boards were reportedly cutting addiction services because of budget constraints.

"That is potentially counterproductive to Government strategy."

He said it was hard to say if there was a shortage of treatment services.

"We do need to improve services in a number of areas, both in terms of geography and in some specific services, for young people, for instance. This is going to be a constant challenge."

Judge Walker, who set up the Youth Drug Court, has started an initiative to bring community resources closer to the court process in Porirua.

"The project is designed to harness the community's resources - this person needs housing, a job, and drug treatment, and bring that to court as a package for an intervention. It's using the court process to deal with the underlying causes."

He said alcohol or drug treatment was not a magic bullet, as addictions often masked other problems.