"Lone wolf" Jami-Lee Ross is expected to go to police today with evidence of alleged donation fraud which he says shows National leader Simon Bridges is a "corrupt politician with no moral compass".
Bridges has called Ross a "liar and a leaker" who is lashing out.
Ross' political career ended in spectacular fashion yesterday when he came out fighting, waiting until his caucus colleagues were meeting behind closed doors to consider his fate before calling a press conference at Parliament with bombshell accusations against Bridges.
Bridges then emerged, flanked by his senior MPs, to inform the media that Ross' former colleagues had unanimously moved to expel him from caucus.
In an explosive press conference, Ross quit the party and called Bridges "corrupt", saying he planned to lay a police complaint over the handling of donations.
Ross claimed Bridges asked him to collect a $100,000 donation from businessman Yikun Zhang in May which was then split into smaller amounts to hide it.
He alleged MP Todd McClay and National Party general manager Greg Hamilton also knew about the donation.
Speaking after Ross' press conference, Bridges said National had kicked "lone wolf" Ross out of the party for his "appalling behaviour".
Bridges said Ross was "lying, leaking" and "lashing out" and he welcomed a police investigation into his claims about donations.
"They are entirely false and I invite Jami-Lee Ross to take them to police. It has zero chance of success, because it is wrong."
Bridges wouldn't say if he knew Zhang or the $100,000 donation, as it was now up to police to investigate.
The National leader repeatedly declined to answer questions about specific electoral donations.
"This is a matter where Jami-Lee Ross has made baseless, false but serious allegations. He should take them to police ... the outcome will be clear and that is I've done nothing wrong."
National Party president Peter Goodfellow yesterday said the party had found no proof of Ross' allegations.
"The allegations made by Mr Ross appear inconsistent with the donor information we have to date, including information previously supplied by Mr Ross," Goodfellow said in a statement.
"We understand Mr Ross will be taking his allegations to the police, and we invite him to do so.
An Electoral Commission spokesperson said it had not received any complaints at this stage but would provide assistance to the police in their inquiries.
Police said they were aware of Ross' claims.
Ross also claimed he was accused of harassing four women.
He said he was marched into Bridges' office about three weeks ago and told of four independent accusations of harassment from women.
He said he was to be stripped of his portfolios and dumped on the backbenches, and when he tried to find out more information about the allegations, Bridges threatened him.
"I asked for details. I was not given any ... He told me if I kept asking for natural justice, that it would not be just four women. It would be 15 women."
A week later he went on sick leave. "It was difficult to accept, and I had a mental breakdown."
National's deputy leader Paula Bennett yesterday refuted Ross' claims that he was accused of harassing women.
"At no point was the matter of sexual harassment ever put to Jami-Lee Ross," Bennett told the Herald.
"What was put to him was inappropriate behaviour that is unacceptable from a married Member of Parliament."
Ross insisted he did not leak Bridges travel expenses to the media – an issue that kicked off the chain of events that led to yesterday's showdown.
But he admitted he leaked a text message about the leaker because he was "floored" by the lack of compassion from Bridges.
He hoped leaking the text message would trigger compassion from Bridges.
"I made a call. I thought trying to get it out publicly ... would offer the person a reprieve."
Ross said he would not sign a privacy waiver so police could confirm his claim he was not the leaker.
Ross said he was now mentally well again but could no longer serve in a political party led by a corrupt politician.
He planned to stand as an independent candidate in the Botany byelection.
"I'm confident I can run on a track record of 15 years."
No other party has decided yet whether to stand a candidate.
In last year's election, Ross won the electorate by a significant margin – winning 21,400 votes to the Labour candidate's 8500.