Police have referred Jami-Lee Ross' complaint about National's election donations to the Serious Fraud Office.
Ross, who was kicked out of the National Party last year, lodged a complaint with police in October.
A police statement today did not refer to Ross by name but said:
"Police have referred to the Serious Fraud Office a complaint received in October last year in relation to the disclosure of political donations under the Electoral Act.
"The complaint has been referred to the SFO as they hold the appropriate mandate to look further into matters raised by the investigation to date.
"While the SFO make their inquiries we are not in a position to make comment on the police investigation."
The Serious Fraud Office investigates serious or complex fraud. It prioritises cases where those allegedly involved are in important positions of trust, or where there are allegations of bribery and corruption.
National leader Simon Bridges has denied any wrongdoing over how the party has handled donations.
He said today that he had not been contacted by police or the SFO.
Bridges said he was not trying to distance himself from the investigation, but was simply noting that the investigation was into the National Party and not him. National's leader said he was completely confident that his hands were clean.
A spokesman for the National Party said neither president Peter Goodfellow nor Hamilton had any comment at this stage.
Ross could not be immediately reached for comment.
Ross went to police in October with details of alleged donation fraud in which he claimed Bridges was a "corrupt politician with no moral compass".
The Botany MP claimed Bridges had asked him to collect a $100,000 donation from businessman Yikun Zhang in May which was then split into smaller amounts to hide it. There is no suggestion of any wrongdoing by Zhang.
Ross alleged MP Todd McClay and party general manager Greg Hamilton also knew about the donation.
Bridges, when the explosive allegations were made, wouldn't say if he knew Zhang or about the $100,000 donation, because it was up to the police to investigate.
Zhang, who owns $40 million in Auckland property, was made a Member of the New Zealand Order of Merit in the Queen's Birthday Honours list.
Ross in October said he believed Zhang had simply been caught up in Bridges' alleged plan to circumvent campaign funding rules.
Ross said Bridges phoned him in May last year, having been at a fundraiser for National list MP Paul Goldsmith, who lives in the Epsom electorate which includes Zhang's home.
"He was excited because he was offered a $100,000 donation from the same wealthy Chinese businessman," Ross said.
"Simon asked me to collect this donation. He was at pains to point out the donation should not be made public and could I ensure this."
Ross said he did as Bridges asked, splitting the money into chunks smaller than the $15,000 limit at which donations had to be declared.
"The full $100,000 donation has not been disclosed to the Electoral Commission."
In October Ross released texts between himself and National Party general manager Greg Hamilton which he claimed showed "National knew about legality issues with the donation back in September".
"I had also been telling them back then that Simon Bridges was the one offered the donation. Their statement that they knew nothing of it was false. I was falsely called a liar by the National Party," Ross said in a message to media at the time.
Ross was kicked out of the National Party after an inquiry fingered him as the leaker of Bridges' travel expenses.
Ross remains in Parliament as an independent MP.
Since his return to Parliament when it resumed in February, Ross has taken on the issue of foreign donations to political parties.
He said donations from foreigners could easily be hidden by being funnelled through a New Zealand-based company or organisation.
"It's a New Zealand company, but you have no way of knowing where the source of the funding has come from. The party only has to declare the donor. It files a return in line with the law if it declares the company."
Ross said thousands, of dollars in donations were put through this way and complied with the law.
"New Zealand political parties should be funded by New Zealanders," he said.