Departing Prime Minister Jacinda Ardern shocked New Zealanders and the world with her stunning resignation today, announcing she has given the job all she has.

But there may have been signs Ardern’s time in the top job had been wearing her thin, when she was caught out calling Act leader David Seymour an “arrogant prick” last year.

Ardern announced today that she would be standing down as Prime Minister in February after being unable to find the energy and heart to continue in the top job.

A caucus vote will unfold on Sunday for a new Party leader and new prime minister with Labour taking the decision to choose a new leader within three days.

But last month, a hot mic in Parliament captured Ardern calling Seymour an “arrogant prick” under her breath.

David Seymour asked the Speaker to have Jacinda Ardern withdraw the remark and apologise. Photo / Marty Melville 1

Seymour had been asking Ardern a series of questions relating to senior Labour MP Nanaia Mahuta’s performance, hate speech reforms and other policies.

But as Ardern took her seat after answering, she could be heard saying to Deputy Prime Minister Grant Robertson, who sits beside her: “Such an arrogant prick”.

Such remarks would ordinarily not be heard, but Ardern’s desk microphone picked up the comment.

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Seymour did not hear the remark himself. It was only after the Herald picked up on the comments and asked Seymour for his response to them that he raised a point of order in the House, noting that Ardern had made an “exceedingly unparliamentary remark”.

Seymour asked that Speaker Adrian Rurawhe have Ardern withdraw the remark and apologise.

Rurawhe did not immediately allow that, noting the remark was not reported in Parliament’s written record Hansard.

However, Seymour’s questioning of the remarks ensured they would be recorded in Hansard for posterity – as interjections that are addressed in the chamber.

Had Seymour said nothing, the remark would have disappeared without a trace.

Jacinda Ardern made the comments to Grant Robertson who sits beside her. Photo / Mark Mitchell

Ardern later apologised to Seymour for the remarks via text and publicly in the House, although she joked that she stood by them.

Referencing another instance when he had been called names by Labour MP Willie Jackson, Seymour told media: “Some days I am a useless Māori, others days I am an arrogant prick.

“The apology we are really looking for is for New Zealanders worried about rising prices and ram raids.

“Jacinda Ardern texted me and said, ‘I apologise. It’s not something I should have said’ and she said, ‘as my mum would say, if you don’t have anything nice to say, don’t say it’.

“I agree with the sentiment and it is all good as far as I am concerned. I just said, thank you and I hope you have a very merry Christmas. At the end of the day, it’s not the end of the world.”

Seymour told Newstalk ZB host Heather du Plessis-Allan he’d been called worse, and he actually saw it as “a victory”.

“I asked her the question … before she said it … can she give us one example where she’d made a mistake, admitted it, apologised and fixed it.

“She couldn’t answer the question which is probably why she was a bit flustered … the great irony is now I actually have got her to apologise for something. So that’s progress. I just wish she’d apologise for a few other things.”

David Seymour and Jacinda Ardern have autographed a printout of Parliament's Hansard recording her calling him an 'arrogant prick'. Photo / Supplied

Ardern and Seymour later smoothed things over, signing a copy of the Hansard page including the comment and auctioning it off to raise money for the Prostate Cancer Foundation.

It sold for $100,100 to a Reefton veterinarian, who said it captured a “moment in New Zealand political history”.

Seymour said last the move was a “very Kiwi resolution to what might be seen as a nasty incident”.