Politicians should discard evidence-based research from "academics and those type of people" when considering criminal justice policy and listen to the public voice, says the Sensible Sentencing Trust's Garth McVicar.

The "tough on crime" advocate spoke out over what he sees as the danger of a return to science-based research and evidence-based policy in criminal justice.

When asked why, McVicar said: "They listened to science for 20-30 years before the evolution of Sensible Sentencing, didn't they, and you couldn't say that worked any which way you twisted it."

His comments follow the release of a heavily-researched, deeply-referenced report published by the Prime Minister's Chief Science Adviser Sir Peter Gluckman into New Zealand's handling of crime and punishment.

It found "tough on crime" approaches had failed, put our falling crime rate down to modern civic, policing and security measures and linked trauma from increasing prison sentences with drivers of violent crime, which is increasing.

It comes as the Government prepares to unveil plans for a "justice summit" after Minister of Justice Andrew Little declared the "tough on crime" approaches followed in New Zealand for decades did not work.

Instead, Little has called for a greater focus on addressing the reasons why people wind up in prison and a greater focus on rehabilitation for those who are jailed.

Our prison population last night stood at 10,588 with projections sending it much higher even as the Government faces a decision on a mega-prison in Waikato alongside its election pledge to cut imprisonment by 30 per cent in 15 years.

In an extraordinary interview, McVicar ridiculed scientifically-backed evidence and said Little faced a "one-term government" if he rolled back law changes which had led to higher rates of imprisonment.

Asked who the Government should listen to McVicar said: "The voice of public opinion. I don't think Gluckman saying [going] back to producing scientific reports and graphs and whatnot ... is proving anything at all." He rejected the research on falling prison rates in the report.

He said: "We've got a high prison population but crime is at its lowest — what's the correlation there? You've locked up the bad buggers. Simple.

"We're seeing the backlash ... now, with the science — as you call it — or the academics or criminologists coming back to have their day."

Little said the growing number of violent offenders and increasing prison population showed that longer sentences and policies such as "Three Strikes" did not work.

Instead, there were mental health, addiction and education issues which led to repeat criminal offending.

Gluckman said the report and others like it were intended to provide the public with information for informed debate. He said it was open to the public and politicians to reject the evidence in the report, with the consequence being an increasingly expensive prison system and a crime rate which would grow.

National Party justice spokesman Mark Mitchell said he rejected the idea that "dogma", as Gluckman phrased the "tough on crime" drive, had driven government policy.

He supported targeting investment at social issues which led to criminal offending and using evidence-based research and statistics to form policy.

McVicar was the focus of controversy recently when he applauded police for saving taxpayer money by shooting an armed, mentally unwell man north of Auckland.