For two weeks last month, Winston Peters told the public he was negotiating in good faith with National and Labour, and asked the public to believe the country's interest was uppermost in his concerns as he weighed up whether to support the incumbent Government for a fourth term, or install a Labour-led coalition.

It turns out he had initiated legal proceedings against leading National ministers the day before the election over the disclosure he had been receiving superannuation at the single rate for seven years while living with a partner.

Peters' lawsuit is unwise on several levels. Most obviously, it reminds the public of a matter treated by all his rivals in the campaign as a genuine, though surprising, mistake.

Surprising, because no MP has taken a more intense political interest in the terms and conditions of NZ Superannuation than Peters over his long career.

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But people do not always pay as much attention to their personal paperwork and his explanation that it was an honest error, which he immediately repaid, was readily accepted - perhaps more readily than Peters himself would accept as an explanation from a political opponent.

Accepting his word, however, does not mean the public had no right to know about the matter. He has filed legal papers not only on former ministers, but also two journalists, a senior public servant and a National Party staffer in an attempt to discover who leaked his personal information.

Peters is not a retired superannuitant. He is a public figure leading a party that, at the time of the disclosure, was quite likely to be in a position to decide who would govern New Zealand for the next three years. A court may find issues of personal privacy and public interest in these circumstances are not clear cut.

It is disturbing that Peters seeks to have journalists reveal their sources through court discovery procedures. He evidently wants the court to order them to hand over phone records, notes and emails relating to his superannuation overpayment.

His attitude to news media going about their job leaves a lot to be desired and may come to pose a threat to press freedom if he now uses his position to try to put his antagonism into law.

But the main reason this lawsuit is unwise is it discredits his post-election negotiations and inevitably reflects on the Government he has chosen. It is now obvious there was extremely little possibility he could work with Bill English, Paula Bennett, Steven Joyce and Anne Tolley since he had initiated legal action against them the day before the election.

Why he put them and the public through three weeks of uncertainty only Peters knows. It is hard to avoid the conclusion it was to increase his leverage on Labour.

Jacinda Ardern is distancing herself from what he is doing, calling it a personal matter for her Deputy Prime Minister. But she can do nothing to dispel a conclusion that the main reason her party is in office is Peters' personal grudge against National over a matter most members of the public might think they had a right to know.