New Zealand First leader Winston Peters says a "disgruntled source" is behind a series of leaks and a serious data breach, and is referring them to police and the Privacy Commissioner.

Peters, who is also Deputy Prime Minister and Foreign Minister, said on Twitter this evening that the information sent to media earlier today was serious.

"The NZF information given to the media this afternoon is a deliberate and malicious misappropriation of data by a disgruntled source," Peters said.

"Despite its age this is a serious breach and as such is being reported to the police and the Privacy Commissioner."

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Earlier today there was another leak of internal NZ First documents, including highly confidential lists of party members and a complaint alleging that local members were ignored in the selection of the 2017 Tamaki candidate.

The latest leak included NZ First's list of party members in Auckland, including names and contact details and whether they were current members.

The list included the contact details of Peters himself, and partner Jan Trotman.

Parties' membership lists and numbers and usually closely guarded secrets, although the party must prove to the Electoral Commission that they have the required 500 members to remain registered as a party.

Some members of political parties prefer to stay confidential because of the roles they hold, such as public servants.

The leaked material also included a mock-up of a hoarding which the source said had been intended for the 2017 campaign, but was vetoed "because of racist implications".

It featured the words: "It's about you, not them."

It is the latest in a series of leaks that have included complaints about donations during the last election that allegedly didn't go where they were meant to, and criticism of Peters for planning to take legal action against National Party figures ahead of Government coalition negotiations.

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Also included in the documents is a February 2018 letter from Julie Carr, secretary of the Maungakiekie and Tamaki branches, to the NZ First board.

Carr said that the board had nominated a candidate to stand in Tamaki for the 2017 electorate without consulting the party's active Tamaki members "in any way".

"We think that was negligent and discourteous of the Board of NZ First to have ignored active Tamaki electorate members in this way," Carr's letter says.

"The Active Tamaki members are upset and disappointed at being ignored in the candidate election process for Tamaki Electorate. We would like the Board to apologise to the Active Tamaki members for ignoring their potentiality for nominating a Tamaki Candidate."

The leaks come in the lead-up to the party's annual conference next weekend and Lester Gray's resignation as party president after refusing to sign off the party's 2019 financial documents.

Before his tweet, Peters told the Herald this afternoon that he was not worried by the leaks "in any shape or form".

He brushed them off and said they would not dampen the spirits of the party as it headed to its annual conference.

"It will have no effect on our convention coming up at all ... It will have no effect on the enthusiasm or the people there, or any such matter."

He questioned if the information was a leak or if it was, in fact, a "breach in our security".

He said NZ First would "deal with" the situation.

"It could be one person, it could be a breach of security – which isn't the first time political parties have had their securities breached," he said.

A previous leak included a laundry list of other complaints about the way the election campaign was run, including how money was used.

In a report titled "NZ First Concerns & Issues Regarding Election", Helen Peterson – who was 20th on the party's list in 2017 – said "members who paid huge amounts of money towards the campaign and promised repayment did not receive any reimbursement".

"Money allocated to support the campaign was not used for the purpose in which it was donated," she alleged in a list of dozens of complaints.

"Members felt exploited as they financed the party's activities with little recognition or reward."