New Zealand prime minister Jacinda Ardern was caught on hot mic calling a rival MP an "arrogant pr*ck."

The incident occurred when lawmaker David Seymour, who leads the libertarian ACT party, bombarded Ardern with questions about her government's performance over the last few years.

Seymour was questioning Ardern during Parliament's Question Time when rival parties get the chance to get into spirited debates. In a video of the incident shared on the internet, Ardern could be heard faintly saying, "He's such an arrogant pr*ck."

Her words were not clearly audible in the Parliament TV broadcast, but were picked up in the official transcript of the debate. Prime Minister Ardern has apologised for the remarks. Seymour told the Associated Press that Ardern messaged him apologising for her language.

"Jacinda Ardern text me [sic] 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 at all.' I agree with the sentiment, and it's all good," he said.

He added that he wrote her back thanking her for the apology and wishing her a very Merry Christmas.

The incident occurs as Ardern prepares for a tough re-election campaign in 2023. Recent opinion polls have put her party, the liberal Labour Party, behind its conservative rivals. New Zealand is expected to hold elections in late 2023.

This is not the first time that a world leader has been put on the spot after their comments were captured by a hot mic. In January, US President Joe Biden was caught calling a reporter "a son of a bitch." The reporter had asked a question about inflation.

In September, South Korea's president Yoon Suk-yeol was caught using profane language for US lawmakers.

"It would be so embarrassing for Biden if those f***ers at the National Assembly don't approve this [bill]," he said in a video posted by South Korean television broadcaster MBC.

New Zealand Prime Minister Jacinda Ardern
Prime Minister Jacinda Ardern. Photo: AFP / Marty MELVILLE