Speaker Trevor Mallard has used the legal immunity of parliamentary privilege to say that a worker - who he apologised to for falsely accusing of rape - had committed sexual assault.

In a debate in the House tonight during the annual review of the Parliamentary Service, for which he is the responsible Minister, Mallard sought to paint himself as on the side of victims and the Opposition as not.

It has prompted National leader Judith Collins to call it "the most extraordinary display" by "the biggest bully I've ever seen in Parliament".

"I've been in Parliament almost 20 years. I've never seen anyone behave like that. I've certainly never seen a Speaker behave like that. He is temperamentally unfit for the role," Collins said last night after the debate.

"He's using women as a shield for his own behaviour. And then he has the effrontery to stand up and say that he defends women. No, he actually is a bully. He needs to go."

National MP Chris Bishop added: "If he really believes what he's saying, he will come out here and say it [without the protection of privilege]. My pick is he won't."

Mallard replied: "I'm prevented by court suppression order and mediation agreement from making comments outside the parliamentary process."

Mallard made the rape claim in media interviews on May 22, 2019, after the release of the Francis report into bullying and harassment at Parliament.

After the former staffer was stood down, Mallard said that a threat to safety had been removed from the premises.

Mallard's false claim cost taxpayers more than $330,000 - including more than $175,000 in legal fees and a $158,000 ex-gratia to the former staffer to settle a defamation claim - and led to the National Party calling for him to resign.

He also apologised to the former staffer for incorrectly using the term "rape" as defined in the Crimes Act.

The former staffer had been the subject of complaints from two women but the complaints were not of rape. An initial investigation into his conduct found no wrongdoing.

Mallard told the House that two complainants had accused the former staffer of sexual misconduct, and overall there were three women, three incidents and "at least two perpetrators of serious sexual assault".

He did not agree that he had destroyed the former staffer's life.

"That man's life was destroyed when he sexually assaulted a woman," Mallard said.

That comment triggered an interjection by National's Nicola Willis: "Say it outside the House."

Mallard said the first internal investigation that found no wrongdoing was a "disgrace" and was done amid a "culture of cover-up".

"The women involved were put back to work with the man who sexually assaulted her. That is the sort of human resources and approach, in my opinion, that belongs in the previous century."

He said it was a judgement call about who to believe - the victims and the police, or the former staffer.

"I start by standing with the victims."

Bishop responded by saying Mallard was a "bully" who had treated the House with "petulance and contempt and hate".

"The minister has used privilege to show the settlement he reached with the plaintiff is not worth the paper it's written on," Bishop said.

Act Party leader David Seymour questioned whether Mallard was "effectively using privilege to venture into an area that is properly the jurisdiction of the courts".

Mallard replied: "I am in no way pretending to be a court. I haven't actually discussed the case that is at the centre of this with the woman involved. I've had no discussion with her at all."

He said he believed the results of the second independent investigation into the complaint.

"And when the police make a decision [on what happened], I will believe that ... That doesn't make someone criminally guilty," he added, noting that police don't always pursue charges for a variety of reasons.

The chamber became tense when Labour MP Willow-Jean Prime said she had heard "horrific statements in the House tonight".

"It really sounds like she asked for it. Her skirt was too short. She was drunk. I didn't like what I heard."

She added "you said it" in response to an uproar from National MPs.

Bishop retorted: "She has just said words that are grossly offensive about Members of the Opposition and she needs to withdraw and apologise. We did not say that."

Prime: "I didn't say you said it."

Bishop interjected again and was forced to withdraw and apologise, as was Prime.

After the debate, Bishop said the short skirt comment was "a made up allegation by a Labour Party that is running cover for a Speaker that they need to be dumping, not defending".

"The real question for Jacinda Ardern is - why is she prepared to tolerate behaviour like we've just seen in the last hour, the vindictive attacks, the use of parliamentary privilege to continue his personal vendetta, the bullying behaviour?"

Ardern has previously said that any issue National has with Mallard was a matter for Parliament, not for the Prime Minister.

Asked how the complainant would see the events of tonight, National MP Michael Woodhouse said that Mallard had re-victimised her to further his own ends.

"She has been re-victimised by a terrible Parliamentary Service process, and a bully of a Speaker who politicised the issue for his own personal gain. I firmly believe he wanted a scalp, he wanted to show himself as the cowboy in this place cleaning up Dodge."

The former staffer quit his job but says he was constructively dismissed - the subject of an ongoing employment dispute.

Parliamentary Service general manager Rafael Gonzales-Montero told a parliamentary select committee in March that he was unwilling to settle the claim because he believed the man had "done something wrong".

Mallard referred to these comments in the House tonight: "[Gonzales-Montero] will not make a settlement because he thinks the message in making a settlement would be that it's acceptable to pay money to people who have sexually assaulted their work colleagues."