Deputy Prime Minister and Foreign Minister Winston Peters has called on Sir John Key to resign as ANZ board chairman, saying he has a "massive conflict on interest".

In the wake of the Hisco scandal, which saw ANZ chief executive David Hisco stood down last week over his personal expenses, Peters says former prime minister John Key should resign from the company where he is chairman of the board.

In an interview on TVNZ's Q+A this evening, the deputy prime minister said he thinks "it's wrong that Mr Key can be head of the ANZ in New Zealand and sit on the Australian equivalent as well".

"That's a massive conflict of interest," he added.

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"And then you've seen the capital requirements, which he's blamed on some low surrogate inside the bank. That again has been wrong."

Peters says he believes there is "much more to be unearthed".

"I think there's some serious questions that need to be answered," he added.

Regarding a potential resignation by Sir John Key, Peters said it is not up to him to decide. "It's the Governor of the Reserve Bank who could make that request. But if you were to ask me if I was the Governor of the Reserve Bank I would have asked for his resignation, yes."

"Because the capital requirements are designed so that we don't end up like for example Greece or Portugal where there are people lined up for kilometres down the street trying to get their money out because the banks didn't have enough by way of reserve," he added.