Controversial right-wing blogger Cameron Slater "categorically refutes" having anything to do with the allegations swirling around Clarke Gayford.
The rumours against Mr Gayford, the partner of Prime Minister Jacinda Ardern, have spread widely in the past week.
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Politik editor Richard Harman says people "on the fringes of the National Party" are to blame for the accusations, and RadioLIVE's Mark Sainsbury says Mr Slater's name has been linked to this.
Appearing on his show on Thursday, Mr Slater says he had nothing to do with the "scurrilous rumours" being spread, arguing he's "no friend of the National Party", and "it'll be a cold day in hell before I do anything to help them". He blames "Labour Party people" for the allegations going viral.
"They're trying desperately to try and hang this on me, but I had nothing to do with it," he says.
"In fact, quite the contrary. People who are associated with me had notified Jacinda personally on February 12 of the seriousness of these allegations. So the Prime Minister has known about them since February."
Ms Ardern says she "won't comment on dirty politics" and would "smile through" the smear attempt. But Mr Slater accuses her of "using a despicable term" coined by a "fiction-writer".
"This is a response finally from the Prime Minister's department, from the Labour Party, but unfortunately they decided to try and make it into a shabby hit-job," he says.
"I categorically refute that I was involved in any way in spreading these scurrilous rumours."
In an unusual move, police released a statement to media saying Mr Gayford is not subject to any police inquiry and has never been charged.
"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," police said.
However Mr Slater says the police were wrong to comment.
"It's politicising the police. Is there anyone else who's ever been cleared of anything," he asks. "This is ridiculous."