On Tuesday, news outlet Stuff reported Mr Nash revealed cabinet disagreements to two businessmen in 2020 over COVID-19 relief for business.

Sacking Mr Nash on Tuesday night, Mr Hipkins also revealed the discussions were to two local party donors: Troy Bowker and Greg Loveridge.

"Stuart Nash has fundamentally breached my trust and the trust of his Cabinet colleagues and his conduct is inexcusable," Mr Hipkins said.

"They are also commercial property owners who had an interest in the Cabinet decision," Mr Hipkins said.

"That crosses a line that is totally unacceptable to me.

"I expect Ministers to uphold the highest ethical standards and his actions raise perceptions of influence which cannot stand."

Mr Nash has not spoken since the allegations were revealed, though Mr Hipkins said he was "gutted".

While Mr Hipkins moved at pace to sack Mr Nash within two hours of learning of the leak on Tuesday, the PM had given Mr Nash a number of chances for previous indiscretions.

A fortnight ago, Mr Nash told a radio station he advised the police commissioner to appeal a sentence - a clear breach of ministerial standards - while also lashing the judiciary for what he saw as soft sentences.

For that blunder, Mr Hipkins stripped Mr Nash of his coveted police portfolio and demoted him down the cabinet ranks.

Mr Hipkins then placed Mr Nash on his "final warning" when it emerged he had used improper channels to lobby for a visa for a medical worker in his Hawke's Bay electorate.

Mr Hipkins indicated the leak would have been enough on its own to see Mr Nash ejected from cabinet.

Opposition leader Chris Luxon called on Mr Nash to leave parliament altogether.

"It's akin to insider trading," he said.

"It's a very serious breach. It just gives you no confidence that he can carry on here in parliament.

"He needs to leave tonight."

The gaffe is a major political headache for Labour ahead of the October 14 election, and may soon become a migraine.

Should Mr Nash resign as an MP before April 15, it will trigger a by-election in Napier, a swing seat in Hawke's Bay.

Mr Nash is a four-term MP and regarded as one of Labour's more conservative caucus members, broadening the party's appeal.

He is also the great-grandson of Sir Walter Nash, a Labour legend, who served as finance minister in the first Labour government and later became prime minister.

Mr Nash's portfolios have been distributed on an acting basis to Megan Woods (economic development), David Parker (oceans) and Meka Whaitiri (Hawke's Bay cyclone response).

Australian Associated Press