Prime Minister Jacinda Ardern says she "absolutely" defends academic freedom, and would act if there was any evidence that China was trying to silence an academic who has been critical of China's influence.

Speaking at her post-Cabinet press conference, Ardern said she was awaiting a police investigation into the burglaries of the home and office of Canterbury University professor Anne-Marie Brady, as well as alleged tampering with Brady's car.

The ongoing campaign of harassment against Brady appears to be linked to her work researching China's foreign policy.

Today an open letter by academics and civil society figures was sent to Ardern and Foreign Minister Winston Peters, calling on them to "be transparent about the outcome of any investigation" and "make a clear statement in defence of academic freedom in light of the Brady case."

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"Be very clear that any intimidation and threats aimed at silencing academic voices in this country will not be tolerated."

Ardern said she couldn't talk about the police case as it was still ongoing.

"Quite frankly, if I received a direct report that said there was an issue there that could be directly attributable to China or at China's direction, we would act on that, but I have not received such information.

"I absolutely defend the right of academics to utilise their academic freedom and, of course, the rights that are granted to them through our legislation. I absolutely support that and defend that.

"They should continue to be able to do their work, and with freedom from repercussion from this Government or any other Government."

A spokesperson for police confirmed that the investigations had not been completed.

"The investigation into the burglaries of Brady's home and office, and the alleged sabotage of her car are ongoing. The burglaries and car investigation are separate investigations, but are linked."

It is understood a secretive branch of police, the national security investigations team typically employed to handle terrorism and espionage cases, is working on the Brady case.

Brady has been an outspoken critic of China and has called on New Zealand to follow Australia's lead in curbing China's influence on domestic affairs.

Her paper Magic Weapons, published last year, detailed what she claimed was a nexus of political donations and appointments of prominent New Zealanders to boards, linked to a broad campaign led by China with the aim of shaping New Zealand policy.

Ardern has said that New Zealand was vigilant to the threat of foreign interference, and has robust measures in place to protect New Zealand institutions.

She has recently confirmed she will not visit China this year because a suitable time could not be found.

"The PM is looking forward to visiting China at the earliest opportunity," Ardern's office said in a statement.

The open letter to Ardern and Peters received support from Green Party MP Golriz Ghahraman and Act leader David Seymour.

"Academic freedoms are paramount to the health of our democracy," Ghahraman said.

"Any evidence of threats or intimidation aimed at undermining academic independence must be taken seriously by the Government."