New Zealand's new prime minister, Jacinda Ardern, has said she regrets sharing a story from her introductory meeting with Donald Trump which led to the accusation the US President mistook her for Justin Trudeau’s wife.

Entertainer Tom Sainsbury told a radio station in Auckland Ms Ardern had confided to him that Mr Trump had assumed she was Mr Trudeau’s partner when the Canadian President introduced the pair to each other at the Apec trade summit in Vietnam.

Mr Sainsbury also said Ms Ardern told him Mr Trump was “not as orange in real life” after meeting him in person at the conference earlier this month in Da Nang.

Ms Ardern was subsequently forced to rebut the claim of mistaken identity, and would only say she told a “yarn” that subsequently spiralled out of control.

Her trip to the trade summit was seen as a test of her skills in representing her country abroad after becoming prime minister last month at the age of 37.

Mr Sainsbury shared the gossip in an interview on The ‘Tea for Two’ show on Auckland-based RadioLive.

He told presenter Ryan Bridge: "I'm not sure if I should be saying this, but she said that Donald Trump was confused for a good amount of time, thinking that she was Justin Trudeau's wife."

He then recounted the claim she had said the US President was "not as orange in real life".

The PM immediately denied the claim the US president hadn’t realised who she was.

"Someone thought the President had confused us, but in all of the conversations we had it was clear to me he hadn't," she said in a statement to Auckland news website Newshub.

Ms Ardern later said that she had shared the “full story” of her meeting with two friends – including Mr Sainsbury – when pressed on the issue by a local news channel.

“I’m in a circle, I am with someone else, I did not hear the full conversation, they observed what they believe to be mistaken identity, I didn’t pick that up,” she told TVNZ host Jack Tame.

“I then had an interaction that suggested he [Donald Trump] knew who I was, that was at the point where I was properly introduced which probably cleared it up.

“Tom’s a mate of mine. I shared a story with him, he shared it with someone else, I can see how that then spirals ... it is a trifling matter.

“It was a bit of a funny yarn, something that I don’t want to cause a diplomatic incident over.