The National Party is continuing its warpath against Speaker Trevor Mallard over his $330,000 settlement with the Parliamentary staffer he alleged was a rapist.

When Parliament resumes on Tuesday National leader Judith Collins will attempt a motion of no confidence in Mallard.

But the move is likely doomed because Labour's massive majority in the House means it can block the motion from being debated.

Shadow leader of the House Chris Bishop said the attempt to out Mallard was "a matter of principle".

"We're very clear that his behaviour is not up to the job of the Speaker.

"It's just simply not appropriate to have the Speaker of the House besmirching the dignity of Parliament in the way that he has and failing to uphold the standards of the House that he himself is in charge of enforcing," said Bishop.

In December Mallard made a public apology for comments he made in 2019 falsely claiming a rapist was working on Parliament's premises. Mallard made the comments following a scathing review by Debbie Francis of Parliament's work culture.

The apology put an end to defamation proceedings lodged by the former staffer. It was then revealed after the House rose that the case cost taxpayers $330,000, including a $158,000 ex-gratia payment to the worker.

Mallard then agreed to a special Select Committee meeting where he again apologised.

At that meeting Parliamentary Service chief executive Rafael Gonzalez-Montero confirmed there was a separate employment case still ongoing which had cost taxpayers about $37,500 so far.

Bishop urged Prime Minister Jacinda Ardern to "put the boot on the other foot" and consider her position if it had been a National Party Speaker who had called someone a rapist.

"He realised he'd made a mistake [within] 24 hours of making the comment and then essentially spent months and months and months refusing to apologise and accept he'd done wrong," said Bishop.

"I'd just ask her, would she really have confidence in that person to lead Parliament? And I think if she's honest with herself the answer would be 'no' and she would be the first person calling for the Speaker to resign."

ACT has not decided as a caucus whether it would support the motion of no confidence but leader David Seymour said Mallard's conduct had caused a lot of damage to the man's life.

"It was difficult to understand why he acted in such a cavalier manner about a serious issue."

Seymour said it was ultimately about who set the standard and the "right thing" was for Mallard to stand down.

Mallard declined to comment for this story.

Te Pati Māori did not respond to the Herald's request for comment while a spokesperson for the Green Party said the matter had no't yet been discussed by its caucus.

Former attorney-general and former National Party MP Chris Finlayson said on NewstalkZB last year that any vote of no confidence would be "ritualistic rubbish" that would go nowhere.

But he said he had "an objection" to MPs being indemnified for defamation suits.

"I think this has all hallmarks of a bit of a mess. If they open their big mouths and they're sued they should pick up the tab themselves."