Since Ardern took office in October, her partner Clarke Gayford, a television fishing presenter, has been subjected to increasingly vicious innuendo and gossip on rightwing blogs, social media and through word of mouth.

On Wednesday, the police commissioner, Mike Bush, issued a press release stating that Gayford is not, nor has never been, subject to a police inquiry.

“While in general we do not respond to enquiries which seek to confirm if individuals are under police investigation, on this occasion we can say that Mr Gayford is not and has not been the subject of any police inquiry, nor has he been charged in relation to any matter,” Bush said.

The prime minister has refused to comment on what she called “dirty politics”.

“It’s just not what I’m here for,” Ardern told the New Zealand Herald.

The Herald reported it had received numerous “tips” about the rumours over recent months, which “also travelled by word of mouth through business, legal, media, political and social circles – and have been published on social media platforms”.

A New Zealand Herald investigation found no evidence that the rumours held any substance.

The political analyst Bryce Edwards said it was unclear whether the rumours were part of an orchestrated political smear campaign or a result of gossip spreading quickly in a small country.

The swiftness with which they spread and were repeated was remarkable, said Edwards.

“It is unclear at this stage if this is an orchestrated campaign and therefore dirty politics or organic ... but there are signs it could be orchestrated.”

He said it was also alarming the rumours “seemed to be more than just a beltway Wellington bubble type scenario ... it actually seems to have gone out from the political community to the wider public, without any mainstream media assistance”.

No other spouse of a New Zealand prime minister had faced the same level of scrutiny and criticism that Gayford had endured during Ardern’s first six months in office, said Edwards. That included a hostile opinion piece by the New Zealand Herald columnist Deborah Hill Cone, calling Gayford “cringey” and “annoying” and accusing him of piggybacking on Ardern’s success.

Edwards said the only other prime ministerial spouse to endure such heat was Helen Clark’s husband Peter Davis, but the scrutiny he faced was still slight compared with what Gayford had experienced.

“Jacinda Ardern is the major asset of this government and it is her reputation, it is her brand, it is her likability and trustworthiness that is underpinning her government’s success,” said Edwards.

“So any opponents will be looking at ways to negatively influence the prime minister’s reputation, and the spouse is going to be a target.”

The prime minister’s office was approached for comment and did not respond.

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