'No to American-style mega-prisons' - Prime Minister Jacinda Ardern

Prime Minister Jacinda Ardern says she's determined to reform New Zealand's justice system, despite Labour's coalition partner New Zealand First striking down hopes of repealing three strikes legislation.

Ms Ardern told The AM Show on Tuesday the Government is still committed to reforming New Zealand's justice system, claiming American-style prison systems "are not New Zealand". 

"We still remain committed to moving away from what has become an American-style justice system where we build bigger and bigger prisons and have low-level offenders in them, and it doesn't necessarily make us any safer," Ms Ardern said.

"I want the people who need to be in prison to be in prison, and the people who should, or perhaps could, benefit from early intervention and rehabilitation to have that. All we want ultimately is an effective justice system, and that's what this debate is about."

The three strikes law was passed under the National-led Government in 2010. It means a person who is given a third strike can be sentenced to maximum prison time without parole. Thirty-eight crimes are listed as strike offences.

But while Labour and the Greens campaigned on reforming this legislation, New Zealand First has long taken a more conservative stance on crime, and opposed the reform.

"Every policy we go through is negotiation by default," the Prime Minister said. "As a coalition Government, we work through every decision and that's not new - most people just aren't aware that we go through that process.

"In going through this process, New Zealand First made it clear they weren't comfortable with three strikes at this point in time."

Ms Ardern said what triggered the conversation around the three strikes law reform was a release of information from the Ministry of Justice before Mr Little was ready to talk about it. Ms Ardern said Mr Little was forced to respond.

"We haven't given up on the need to have this conversation, because as I've said from the beginning, when you have a crime rate that is pretty much static, but you have an ever-increasing prison population, I think it's incumbent on you as a Government to look at what's going on."

She said the Government will announce plans on Wednesday for the refurbishment of Waikeria Prison. A report in May revealed several faults at the prison, including long lock-up times, understaffing and a lack of a fence.

Prisoners in the at-risk unit were found to have spent up to 22 hours of a day locked in their cells with little to engage them, and up to 26 hours at a time between their cell being unlocked. One prisoner mentioned they had become fixated on self-harm during their time in the unit due to the lack of other activities to engage their mind. 

"Waikeria is not in good shape," Ms Ardern said. "I visited it a couple of months ago and it's one of our most tired prisons.

"You do want to make sure that when you have people incarcerated that you've got some decent facilities and that is not a decent facility."

She said the Government will be bringing in experts to help them with justice reform, of which details will be announced soon. Mr Little will be running a summit in August to get people involved with justice policy to discuss new ideas and possible avenues to take with justice reform. 

Prison populations are projected to soar to over 12,000 by 2022.