Winston Peters is "welcoming" the Electoral Commission's decision to refer an investigation into the New Zealand First Foundation to the police, after its finding that donations to the organisation "should have been treated as party donations".
The police have now referred the investigation to the Serious Fraud Office (SFO).
The Electoral Commission issued a statement on Monday confirming that enquiries had been made into allegations the New Zealand First Party tried to hide donations through the New Zealand First Foundation.
The allegations were made in a Stuff report in November 2019, citing documents that raised questions about financial exchanges between the New Zealand First Foundation and New Zealand First Party.
"Based on the information available, we have formed the view that the New Zealand First Foundation has received donations which should have been treated as party donations for the New Zealand First Party," the commission said.
"In the commission's view, the donations were not properly transmitted to the party and not disclosed as required by the Electoral Act 1993."
The Electoral Commission does not have the investigative powers to determine whether offences have been committed so the matter has been referred to the police.
The commission said the police will "have the necessary powers to investigate the knowledge and intent of those involved in fundraising, donating, and reporting donations".
A police spokesperson said the matter has now been referred to the SFO.
An SFO spokesperson said: "The Serious Fraud Office expects to receive a referral from NZ Police in relation to the New Zealand First Foundation. The SFO will be assessing the matter and has no further comment at this time."
New Zealand First leader Winston Peters has denied any wrongdoing, and described the claims raised in November as "filthy allegations without any proof".
He told Magic Talk in November all of the loans the New Zealand First Party received from the foundation had been paid back, and he said those making the donations are entitled to privacy.
Peters announced on Sunday he had asked his party president to prepare a police complaint over the "massive breach" of the party's information.
"This morning I have recommended to the New Zealand First party president that she begin preparing a complaint to the police over the massive breach of New Zealand First's party information," he said.
"New Zealand First has so far been sensitive to the circumstances surrounding the theft of party information but can no longer tolerate the mendacious attacks against the party and its supporters."
The documents obtained by Stuff purportedly showed that the New Zealand First Foundation collected more than $500,000 in donations in two years.
The money, allegedly used for party expenses without being declared, included $38,000 on the New Zealand First Party's campaign headquarters, Stuff said.
Peters said in a statement on Monday that New Zealand First welcomes the Electoral Commission's referral to the police, saying it "confirms our prior view that only the police would have the powers to determine the issues involved".
He added, "In light of the Electoral Commission's findings today the New Zealand First Party can also confirm it will be reviewing its arrangements for party donations.
"This party is built on the support of loyal supporters and donors and believes it has followed the law implicitly."
"I am advised that in all its dealings the Foundation sought outside legal advice and does not believe it has breached the Electoral Act.
"At this stage the SFO will consider if an offence has been committed, or otherwise, and it is not appropriate to make any comment on specific detail that prejudges their investigation."