She said that “the claim that it was an exclusive interview for the purpose of writing a book of that nature [a biography] is not true”, and said she would ask that the claim be clarified.

Harte denied the claim she was misled, saying Ardern’s office was later made aware the book’s framing had changed to become a biography.

The spat comes at a moment when presentations of Ardern in international media – often glowing - are under particular scrutiny in New Zealand. A proposed film about the Christchurch mosque attacks, called They Are Us and starring Rose Byrne as Ardern, has been fiercely criticised over accusations that Muslim victims have been sidelined in favour of a focus on Ardern.

Ardern said on Sunday she was not an appropriate focus for a film about the 2019 mosque attacks. “There are plenty of stories from March 15 that could be told, but I don’t consider mine to be one of them,” she said. Ardern reiterated that she has no involvement with the film.

In a statement to the Guardian, Harte confirmed the original interview was for a book profiling a number of female leaders. “Prime Minister Ardern was, however, not misled, because at the time of the interview, we had no intention of writing a biography on her alone,” he said.

Harte said they shifted tack to a biography of Ardern after Covid-19 precluded plans for interviews with other world leaders, and because “her story deserved a book in itself, for her model leadership”.

“Our decision to change direction – something that, I must say, is the hallmark of many creative endeavours – was made in 2020.”

He said Ardern’s office was aware the book’s framing had changed to biography, saying that in January, Vani had “informed the prime minister’s office of our intention to publish our biography of Jacinda Ardern, and shared the cover”.

“We regret the misunderstanding,” Harte added. “We stand by our book”.

Vani did not provide independent comment, but said she would refer the request to her co-author.

The book’s claims of exclusive interviews with the prime minister raised some eyebrows in New Zealand, because Ardern does not typically grant interviews to biographers. Two senior New Zealand journalists, Madeleine Chapman and Michelle Duff, have written biographies of Ardern. Neither were able to secure an interview.

A brief excerpt from Vani’s interview was published by Vani in a Writers Digest article about how to write and research a biography. Vani asks: “I feel that you laid the foundation of your personality when you instantly empathised in your own childhood with the children on the streets of New Zealand without shoes on their feet or anything to eat. Would you agree with me that you could observe all these things because you were born an empathetic person”? Ardern responds, “I would like to believe that it is something that is an inherent trait for all of us. It’s about having the space to be empathetic.”

Simon & Schuster quote Booklist as having called the book a “readable, admiring biography”. In a review for the Spinoff, Toby Manhire calls it “utterly uncritical, fawning, cloying”.

A passage describing Ardern’s outfits on her visit to Europe reads: “In London, she upped the ante, featuring perhaps the most graceful, regal attire ever worn by a New Zealand prime minister at an international event.”

It goes on: “The effect was breathtaking … Even the Queen looked impressed.”

Another compares her favourably to the great British wartime leader Winston Churchill because of her response to the pandemic. “If there is a Winston Churchill of the war against Covid-19, for her success in rallying her country to fight the virus, there’s a good argument to say it’s Jacinda Ardern.”

The book is sold by Simon & Schuster and appears to have multiple publishers across different jurisdictions, including Harper Collins India, Hardie Grant in Australia and New Zealand, and Oneworld Publications. The Guardian has approached Simon & Schuster, Oneworld Publications, Hardie Grant and Harper Collins India for comment.