New Zealand police minister resigns after radio gaffe

New Zealand's police minister has resigned after revealing in a radio interview he asked the police commissioner to appeal a sentence.

Napier MP Stuart Nash has lost the police portfolio over the indiscretion, which he revealed on Newstalk ZB on Wednesday morning.

In a discussion about crime levels, Mr Nash revealed his intervention and criticised the judiciary, suggesting judges should levy harsher sentences to gang-related crime.

"This bloke didn't have a licence, had illegal firearms, had illegal ammunition and had guns without a licence and he got home detention ... That was a terrible decision by the judge," Mr Nash said.

"I phoned up the police commissioner and said, 'Surely you're going to appeal this?'

"Judges need to read the room on this. Society is sick to death of these gang members creating havoc."

Crime is a top-level political issue in NZ, where gangs have grown in size, partially due to Australia's practice of deporting Kiwi criminals en masse.

Prime Minister Chris Hipkins said while Mr Nash was not police minister at the time of the incident in 2021, he had breached the cabinet manual for his lack of professionalism and for involving himself in a particular case.

"The minister has reflected on his actions and agrees it is no longer tenable for him to hold the police portfolio," Mr Hipkins said.

Mr Hipkins said contacting the commissioner was "unwise" and Mr Nash's reflections on the judiciary were "an error of judgment".

"He had already offered via message to me that he would tender his resignation so he conversation was relatively short," he said.

"Had he not offered his resignation I would have removed him from the role."

Mr Nash - ranked 11 in cabinet - retains the economic development, forestry, and oceans and fisheries portfolios.

Both the opposition National party and right-wing ACT party, which highlighted the breach, called for Mr Nash to be sacked from cabinet.

"He interfered. He boasted about it. And then he doubled down on it. That's three strikes and Stuart Nash should be out," ACT leader David Seymour said.

The 55-year-old Mr Nash, who served as police minister in Labour's first term under Jacinda Ardern, was moved out of the portfolio in 2020 and shuffled back in when Mr Hipkins became leader this year.

Earlier on Wednesday, Mr Nash downplayed the seriousness of his comments, describing his conversation with commissioner Andy Coster as "chewing the fat with a guy who was a mate".

Acting opposition leader Nicola Willis, standing in for COVID-struck leader Chris Luxon, said the sacking was "the right thing to do".

"There are some principles in our democracy that all sides of parliament agree to, and we all agree that independence between ministers in the police is really important and I'm glad to have seen that upheld," she said.

Energy Minister Megan Woods will act as police minister until Mr Hipkins appoints a replacement for Mr Nash.