MP Jami-Lee Ross has released a recording of a phone conversation between himself and National Party leader Simon Bridges discussing a $100,000 donation from Chinese businessman Zhang Yikun.

The Serious Fraud Office is filing criminal charges against four people in relation to donations to the National Party.

But party leader Simon Bridges says neither he or the party has been charged.

The four are scheduled to appear in Auckland District Court on 25 February, according to a press statement by the office.

KEVIN STENT/STUFF Jami-Lee Ross was a former top ally of Simon Bridges.

"The Serious Fraud Office filed criminal charges today against four people in relation to donations paid into a National Party electorate bank account," the statement said.

The complaint against the National Party and its leader Simon Bridges was referred to the Serious Fraud Office by the police in March of last year.

Police received the original complaint from former National MP Jami-Lee Ross in October of 2018, in the middle of his explosive departure from the party.

SUPPLIED The Serious Fraud Office has been looking at the case since March of 2019.

Ross alleged that Bridges asked him to break up a $100,000 donation from a wealthy Chinese donor into smaller chunks in order to get it under the $15,000 donation threshold in the Electoral Act.

He provided police with a recording of a secretly-recorded conversation between him and Bridges where a $100,000 donation was discussed.

Bridges has repeatedly denied any allegation of wrongdoing.

He told media last March that the complaint was a matter for the National Party and he expected it to cooperate.

In a statement on Wednesday, Bridges said he and his party secretary had not been charged.

"I have always maintained I had nothing to do with the donations. As I have always said the allegations against both myself and the Party were baseless and false," Bridges said.

"This was always just a vendetta by a disgruntled former MP."

Party general manager Greg Hamilton said the party was keen to put the matter behind it was confident in its processes.

Ross has been contacted for comment.