National's MP for Botany, Jami-Lee Ross, will be laying an official police complaint against National Party leader Simon Bridges tomorrow, in which he'll allege electoral fraud.
Mr Ross also told media this morning he would resign as a member of Parliament on Friday, sparking a by-election for the Botany seat.
Mr Ross said he would run as an independent.
Today he followed up on allegations of unlawful activity from Simon Bridges over electoral donations.
In a news conference shortly afterwards, Mr Bridges dismissed the claims as "baseless", and encouraged him to report the matter to the police.
'I have done absolutely nothing wrong," he said, but would not directly address Mr Ross' allegation.
He said the party would not tolerate his behaviour, and he would be expelled.
Mr Ross said: "Simon Bridges knows exactly what Cathedral Club is. It is a name used to hide a donation from a close friend of his. He claims it was a clerical error, I claim BS on that."
"I believe Simon Bridges is a corrupt politician."
He later added: "On Monday 14th of May this year, I attended a dinner with Simon Bridges at the home of a wealthy Chinese businessman.
"The following week ...Simon called me in the evening he'd been at a fundraiser with Paul Goldsmith.
"He had been offered a donation $100,000 donation from the same wealthy businessman."
Mr Ross alleged Mr Bridges did not want the donation to be public, and asked Mr Ross to ensure it.
"I duly carried out Simon Bridges' wish."
He said it was split into smaller donations.
Mr Ross then said he had a recorded conversation with Mr Bridges about the alleged events.
Mr Bridges' office has previously directed media questions about the Cathedral Club to the party.
A spokesperson told Radio NZ yesterday that the donation error was down to the local Tauranga electoral committee and said the Electoral Commission was contacted to seek advice. The return was then amended and re-submitted.
Mr Ross' remarks this morning came a day after Bridges outed him as the likely leaker of his expenses, following the completion of a PWC report into the leaking.
"I'm standing up for what I believe in. New Zealand deserves better from the National Party," Mr Ross said today.
"I’m now the subject of a smear campaign.
"Simon is a flawed individual without a moral compass."
After taking sick leave earlier this month, Mr Ross said today he had had a mental breakdown but was now in good health.
He claimed the PWC report was inaccurate, and the only time he messaged the journalist who released the National Party expenses was when they texted him to ask how he was.
Mr Bridges yesterday denied all of Mr Ross' accusations and said: "He would say those things, given the situation."