In an extremely unusual move, police have released a statement clearing the name of Clarke Gayford, the partner of Prime Minister Jacinda Ardern.
It comes after a vicious rumour was started about Mr Gayford.
"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."
After the police statement was released, Newshub and other media received a letter from Mr Gayford's lawyer Linda Clark saying the allegations "are untrue and defamatory."
"The article confirmed via a statement from NZ Police that Mr Gayford is not and has not been the subject of a police inquiry and has never been charged in relation to any matter.
"This letter puts you on notice that any publication of the substance of the allegations regarding Mr Gayford (which he denies and which are untrue) will be actionable."
Ms Ardern told Newshub she did not want to comment.
"I won't comment on dirty politics. It's just not what I'm here for."
The rumours have spread widely, with Newshub reporters receiving a number of inquiries from members of the public.
The National Party says it has nothing to do with the false allegations.
"As Leader I've repeatedly made my expectations very clear – National MPs will not be involved in peddling rumours or innuendo," Opposition leader Simon Bridges said.
"It is my expectation that they will be conscious of their dealings with media, and ensure they are above reproach."