The Serious Fraud Office has laid charges after an investigation into donations made to the Labour Party in 2017.

The agency filed criminal charges yesterday against six people in relation to a donation made to the Labour Party.

"The defendants are entitled to seek name suppression therefore the SFO will not be naming any defendants until any name suppression issues have been resolved," the SFO said.

"We note, however, that none of the defendants are sitting MPs or are current or former officials of the Labour Party."

Responding to the filing of charges, Labour Party General Secretary Rob Salmond said: "The SFO has announced today that no sitting MPs and no current or former Labour Party officials have been charged in relation to their recent investigation."

"The Labour Party has complied with the law," he said.

"Labour has not sought any suppression orders from the Courts.

"As the matter is before the Courts, we won't be making any further comment."

When the SFO announced its investigation in July last year, Labour Party president Claire Szabo said: "We have not been advised of the specifics of the inquiry, however the Labour Party will fully cooperate with any SFO investigations."

The then minister responsible for the SFO, Stuart Nash, also said he was blindsided by the agency's announcement.

"I had no indication whatsoever that anyone was looking to investigate us, so I don't know who has lodged a complaint with us but, you know, time will tell."

The financial crimes department has remained tight-lipped over the details of its investigation.

Another SFO prosecution, involving donations to the National Party, is due to go to trial in September.

Former MP Jami-Lee Ross and a trio of businessmen were charged in January last year with obtaining by deception. They have all formally denied the allegations over donations of $100,000 in 2017 and $100,050 in 2018.

Meanwhile, two people charged by the SFO over allegations of improper political donations involving the New Zealand First Foundation continue to enjoy interim name suppression.

A hearing to determine whether their identity will be made public will be held in June, while a trial has been scheduled for next year for the pair accused of obtaining by deception.

In December last year, Judge Deidre Orchard in the North Shore District Court initially dismissed an application for continued suppression but this was appealed by the first defendant.

Suppression has been opposed by the SFO and a consortium of media organisations, including the Herald's publisher NZME, which unsuccessfully attempted to name the pair before last year's election.

The NZ First Party also attempted to stop the charges becoming public until after a government was formed.

NZ First leader and former Deputy Prime Minister Winston Peters has distanced himself from the foundation and has denied any wrongdoing after it first came under scrutiny in November 2019.

After the charges became public, Peters also claimed at a press conference he and the party had been "exonerated".

Just last month, police also referred an inquiry over donations to the Māori Party to the SFO for further investigation.

The Electoral Commission had previously referred the matter of party donations totalling $320,000 to the police.

An SFO investigation into Auckland Mayor Phil Goff's election expenses is still ongoing, while a probe into his former Labour Party colleague and Christchurch Mayor Lianne Dalziel was closed in December with the SFO declaring there was no evidence of any criminal conduct.

Both matters were referred to the SFO by police.