The government confirmed on Thursday it is scrapping an already expired prison reduction target and will no longer fund the cultural reports used in sentencing.

It says it is "making good on its promise to restore law and order" in New Zealand, but the Green Party says the decision will cause "significant harm" to Māori in particular.

The moves were earlier announced as part of National's 100-day plan, but were confirmed by the government after a Cabinet meeting on Thursday.

Justice Minister Paul Goldsmith says the Section 27 cultural reports cost taxpayers more than $7 million in the last financial year and led to shorter sentences.

Goldsmith says the reports had become a "cottage industry costing taxpayers millions and doing nothing for the victims of crime".

The government will introduce a bill in the next Parliamentary session - which starts next week - to exclude the reports from legal aid.

Speaking to media after Thursday's Cabinet meeting, Prime Minister Christopher Luxon says there is still the opportunity for anyone to bring someone who can speak to their past into the courtroom, but there would not be funding for written reports.

"Over time it's become professionalised," he says.

The government's announcement also included confirmation "that the Government has scrapped the previous Labour government's target of reducing the prison population by 30 per cent".

However, Labour leader Chris Hipkins confirmed during last year's election campaign that target was from the previous term, and the party would no longer have such a target.

Corrections Minister Mark Mitchell says there should only be fewer people in prison if there was a drop in serious offending.

"This government is determined to put public safety back at the heart of the criminal justice system," says Mitchell.

In September, Mitchell had celebrated Hipkins' announcement: Labour "will finally ditch its disastrous target to reduce the prison population by 30 percent".

Luxon on Wednesday says it had at the time been "pretty hard to work out what was being committed to" by the previous government.

"Whether that was announced in the death throes of the campaign where there was lots of desperation going on from the Labour government ... I don't know," he says.

"I'm unclear whether the target was in place, I remember through the campaign there was rumours it might not be, but it had obviously been a long-standing policy and practice of the previous administration."

Luxon says the government now was being very clear they were not going to carry on what was seen in the past six years.

He says the government was working on a complete set of targets, including on youth crime, violent crime, and reducing time taken through the justice system, and would have more to say on that in due course.

National has also committed to further legislation to cap jail sentence discounts at 40 per cent.

Thursday's announcement has been welcomed by the ACT Party, with justice spokesperson Todd Stephenson saying the party had pushed to scrap Section 27 reports entirely.

"ACT's coalition agreement secured the defunding of Section 27 reports and exploring further reform of how these reports are used. We also secured the commitment to abolish Labour's prisoner reduction target and reform the Sentencing Act 2002 to give greater weight to the needs of victims and communities over offenders."

But the Green Party says Māori in particular faced "significant harm" from the decision.

Courts spokesperson Tamatha Paul says the government was taking New Zealand "further away from a justice system that treats everyone with humanity, dignity, and respect".

"While pre-sentencing background reports are available to anyone, the ongoing and heartbreaking over-representation of Māori in our courts means that it is our people who will be hurt the most."

Paul says without the sort of information included in a cultural report, the risk of future offending is likely to be higher than it would be otherwise.

"We need a government that will work toward a justice system that restores mana to our people and communities and heals the harms of intergenerational trauma. A government that will create meaningful alternatives to putting people in prison."

RNZ