Deputy Prime Minister Winston Peters has taken the stand in his legal battle against the Crown, describing the "malicious leak" of information about his superannuation to media.

At the High Court in Auckland, Peters is suing the Attorney-General on behalf of the Ministry of Social Development (MSD), the ministry's chief executive, the State Services Commissioner and former National Party ministers Anne Tolley and Paula Bennett.

His case alleges a breach of his privacy in the leaking in 2017 of his seven-year national superannuation overpayment.

On Monday, Peters told the court details of his superannuation payments should never have reached the ministers, and claimed the leak to journalists was a deliberate attack on his reputation.

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"It is still brought up by my detractors as a slur on my character to this very day," Peters said.

"There was no scandal, just a malicious leak which mixes fact with a deliberate falsehood.

"They [those who leaked the information] simply had no basis to disclose to the minister. This [superannuation] is not a matter of significance, given there were 23 such similar issues in the month before this issue, which were not reported to the minister."

The deputy PM was then cross-examined by the lawyer acting for the ministers, Bruce Gray QC.

Gray suggested Peters' overpayment issue was being dealt with "broadly around the same time" former Green Party co-leader Metiria Turei admitted to benefit fraud in July 2017.

"No, [it was] after my problem had arisen, and well after action had been taken. If she was the excuse, it fails because the action had already been taken," Peters replied.

"It is not a sanctuary to which they can go, and I think it's one sir, which with respect, they've dreamt up with hindsight."

Gray also said the minister "ought to be interested to know" that Peters, as a politically prominent person, was receiving the same treatment as any other New Zealander from MSD.

"I'm entitled to privacy as much as anybody," Peters said.

MINISTERS 'SOUGHT TAXPAYER FUNDING'

The cross-examination continued into the afternoon, with Gray putting it to Peters that he was asking the court to award him "a lot of money, mostly paid by private individuals".

Peters responded by saying it was the people he was suing who were opting to use taxpayer funds to defend themselves.

"I am putting the money up here, putting it all on the line because I believe in a principle here, and they have immediately sought taxpayer funding of their defence."

The deputy PM claims the government departments and officials breached his privacy in advising the ministers of his superannuation. Further, he has accused the officials of being reckless and acting in bad faith, which the Crown denies.

He wants $450,000 in damages from each of the named defendants, meaning a total of $1.8 million if he pursues all of those monetary claims listed in early court documents.

Any damages awarded would be covered by the taxpayer under an arrangement authorised by the Cabinet. Taxpayers are also paying for the Crown's Victoria Casey QC and the ministers' Bruce Gray QC, and legal teams.

Some of the witnesses called by Peters in the case have been granted interim name suppression until the conclusion of evidence.

Peters was acting prime minister on Monday while Jacinda Ardern attended the East Asia Summit in Bangkok.

Ardern will return on Tuesday.