Steven Joyce on who's behind Winston Peters' super leak

Steven Joyce has handed in his resignation but can't resist handing out a few last political hits.

Speaking on The AM Show on Wednesday morning, the former National Party Finance Minister said he believes a Green Party sympathiser is behind Winston Peters' superannuation leak.

"I think it was probably somebody who didn't like... somebody in the system somewhere who didn't like the way Metiria Turei was treated and decided to try and even up the score in their own way. That's my suspicion. I have no basis for it," Mr Joyce said.

He said he only found out about the overpayment when the story hit the news, claiming it would make no sense to leak the information and give Mr Peters airtime during the important campaign period.

"From a political point of view, this guy was out of the media because Jacinda Ardern was sucking up the oxygen. Why would you possibly want to give Winston Peters, the wily politician who will use anything to his benefit, any sort of suggestion of getting himself another platform a couple of weeks out from the election?" he asked.

During the election campaign, a source told Newshub Mr Peters had been overpaid thousands of dollars of superannuation payments.

Winston Peters in Parliament.
Winston Peters in Parliament. Photo credit: Getty

Newshub reporter Lloyd Burr called Mr Peters with questions. Shortly after that Mr Peters sent out a press release admitting there had been an "error" in his superannuation, "leading to a small fortnightly overpayment".

After the coalition deal was struck in late October, Mr Peters launched legal action against senior National Party Ministers Bill English, Steven Joyce, Anne Tolley and Paula Bennett, as well as National's former chief of staff Wayne Eagleson, National campaign staffer Clark Hennessy and two journalists - Mr Burr and Newsroom's Tim Murphy.

Under the no surprises policy, Ms Tolley and Ms Bennett National Party Ministers had been informed of Mr Peters' overpayment.

Mr Peters says action against the two journalists has been "amicably resolved."

Newshub.