Should New Zealand treat misogyny as extremism?

New Zealand should consider following the UK's lead in classifying a form of misogyny as extremism, an expert says.

Politicians have also weighed in, with one saying she does no want to see restrictions on free speech.

It comes as the UK home office undertakes a review of its counter-extremism strategies in an attempt to crack down on harmful ideologies online and offline.

University of Auckland senior lecturer Dr Chris Wilson said extreme misogynistic violence was increasing globally.

"The abuse that you see online appears to be increasing, there have been a growing number of violent events that appear targeted at women."

He said the Bondi Junction mall attack in which Joel Cauchi killed five women and one man and injured nine women and two men, was an example.

New South Wales police Commissioner Karen Webb told the ABC in the aftermath of the attack: "It's obvious to me, it's obvious to detectives that that seems to be an area of interest, that the offender had focused on women and avoided the men."

Police in the UK have described the threat of self-described misogynist influencer Andrew Tate to radicalise young boys as a "national emergency".

The UK government is now considering classifying extreme misogyny as a form of extremism in its strategies to target harmful ideologies.

Wilson said New Zealand should consider doing this too.

"This is not about curtailing free speech, or placing sanction on people for saying particular forms of speech, it's about being able to identify those individuals that appear to be on a path toward violence, it's about being able to take action when it needs to be taken, it's about the allocation of agency resource."

A New Zealand Security Intelligence Service spokesperson told RNZ the agency already considers violent misogyny under its existing framework.

There are four categories of extremism, politically motivated violent extremism, faith motivated violent extremism, identity motivated violent extremism, and single-issue motivated violent extremism.

But Wilson said extreme misogyny deserved its own category so more resources and attention could be directed at stopping it.

He said 26-year-old Caleb Bell, who drove his car drunk into two teenage girls at an Epsom bus stop last year, telling police it was because he did not have a girlfriend, could be an example of incel violence.

He also believed misogynistic threats against female leaders in New Zealand were increasing.

"We saw with Jacinda Ardern the number of death threats; I think nine were actually brought to court.

"I mean that's a major indicator - no male colleagues get that."

RNZ approached two female academics to speak on misogyny and extremism, who said they could not out of fear of the abusive backlash they would get.

Porirua mayor Anita Baker said she got death threats a couple of years ago when she tried to introduce a paid parking rule in the city.

She said she tried to push it to the back of her mind but it changed the way she lives.

"I don't like going home at night by myself, you know, if my husband is away and I am more cautious now at night when I am out, I don't want to walk distances by myself."

She said it was often difficult to deal with the constant flow of misogynistic abuse when it was sent anonymously online.

Finance Minister and deputy leader of the National Party Nicola Willis agreed.

"The b word and the c word, those words don't get thrown around for men and they are inherently, I think, sexist words.

"I'd also observe that the people who often make these attacks hide themselves which I think demonstrates that they know that expressing themselves in that way is socially unacceptable, but they go ahead and do it any way."

But she was hesitant to follow the UK's lead in classifying a form of misogyny as extremism under any law change.

"I'm inherently uncomfortable and cautious when it comes to any form of censorship or restrictions to free speech. I think we have to be very careful before we embark on any path like that.

"And I sincerely think that right now one of the most powerful things we can do to stop this behaviour is simply calling it out."

A New Zealand SIS spokesperson said the agency was well aware of the abhorrent misogynistic views being spread in the community every day, particularly online.

The spokesperson said the vast majority of violent extremist threats made online were not acted on, but that the agency worked with police to investigate individuals and groups which could pose a threat to national security.