'Tough on crime' rhetoric really doesn't work' - New report suggests switching from punishment to prevention in NZ's justice system

A new report says New Zealand's prison system needs a significant overhaul to tackle the increasing prison muster.

The report, authored by Associate Professor Ian Lambie and Sir Peter Gluckman, shows our prison population is rising despite a decrease in crime rates.

The authors concluded that the rising costs of prison to New Zealand taxpayers was "not due to an increasing crime rate, but rather because of successive policies that have been implemented so as to be seen to be tough on crime".

"Evidence suggests that we are not making potential victims safer by responding in a blunt and an overly punitive manner," the report said.

"To reduce crime, a better justice system requires evidence-based, cost-effective approaches to prevention, intervention, and rehabilitation, not just imprisonment."

Speaking today on TVNZ 1's Breakfast, Dr Lambie said many of those in the criminal justice system are affected by mental health and addiction issues, and that it begins at a young age.

With prisoner costs averaging about $100,000 per year per prisoner, "the 'tough on crime' rhetoric really doesn't work and I think we need to get smart on crime," Dr Lambie said.

"It really should focus on early intervention ... when it's cost-effective.

"What does the science say for the best way to intervene and actually help people in the system?"

Justice Minister Andrew Little has told The Press that "our spending on prisons and criminal justice system has been the fastest-rising area of government spending".

"We could use that money in better ways for people to prevent them getting into prison," Mr Little said.

"We just have to think more carefully about how we are spending our money, where we invest things in the criminal justice system.

"We just haven't had the national conversation ... we say 'lock 'em up, lock 'em up, be tough on crime' - but all that's going to do is keep driving up costs."

Dr Lambie said a "public discussion" or "summit" is needed to discuss exactly how the new justice system should work.

"The government has clearly indicated they want some work done and are interested in reform," Dr Lambie told The Press.

"Where we are heading is not where we should be, and it does not create a safer society, a safer New Zealand."