The Serious Fraud Office (SFO) is pursuing criminal charges over an alleged $100,000 donation to National, but not against the party or its leader Simon Bridges.

Photo: RNZ / Dom Thomas

The agency launched an investigation in March 2019 into National Party donations, after police referred on a complaint made by former National MP Jami-Lee Ross.

In a statement, the SFO confirmed it would be pursuing charges against four individuals, but did not name them.

"The defendants are scheduled to appear in the Auckland District Court on 25 February," a spokesperson said.

"The SFO will not make any further comment until any name suppression issues have been dealt with."

The National Party promptly issued a statement, confirming neither Bridges, nor the party, were among those 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."

National general manager Greg Hamilton said he had always been confident in the way the party received and declared donations.

"We are happy to put this matter behind us and will not be making any other comment," he said.

Ross - who is now an independent MP - has been approached for comment.

He dropped the bombshell allegations in October 2018, claiming Bridges had asked him to collect a $100,000 donation from a wealthy businessman.

He said Bridges had stressed it should not be made public. The money then arrived in chunks smaller than $15,000, the threshold at which donations have to be declared, Ross said.

Both Bridges and the National Party have consistently denied any wrong-doing.