National leader Christopher Luxon says Stuart Nash should leave Parliament immediately after he was sacked from Cabinet.
Prime Minister Chris Hipkins on Tuesday night dismissed Nash from his portfolios after an email came to light in which he shared confidential information about what happened in Cabinet with two of his donors.
Hipkins said this email was a "clear breach of collective responsibility and Cabinet confidentiality" and it "crosses a line that is totally unacceptable to me".
There is nothing to suggest the two donors who received the email from Nash did anything wrong.
Speaking immediately after the Prime Minister, Luxon said this is an "incredibly serious and egregious issue".
"It's akin to insider trading. Frankly he shouldn't just be gone from Cabinet, he needs to be gone from Parliament," said Luxon.
In a statement, ACT leader David Seymour said Hipkins will now pay the price for having "low ministerial standards".
"Hipkins said he asked for an assurance that Stuart Nash had done nothing else that would breach the Cabinet manual and got that assurance. He clearly did a poor job of it."
And Luxon accused Hipkins of letting issues with Nash slide three times before.
"I'm sorry but we have standards here. This is a very senior minister. This is his fourth contravention of the Cabinet manual. Chris Hipkins finally faces up to it tonight," Luxon said.
Asked if there should be a wider investigation into Nash's behaviour, Luxon said: "I think there are a lot of questions that you will no doubt start asking about what other issues have gone on, what other possible leaks may have happened."
An immediate resignation would trigger a byelection in Nash's Napier seat, which would cost taxpayers hundreds of thousands of dollars just six-and-a-half months out from a general election.
"If he resigns tonight, which is what should happen, the consequences will be what they will be," said Luxon.
"He needs to leave tonight. It's that simple. The breach is so serious and so egregious and such a big breach of Cabinet manual on so many levels that you cannot trust having Stuart Nash in your caucus."
Luxon said National's candidate Katie Nimon would do a far better job for Napier and National is ready for a by-election.
"Based on what we have seen this evening, he cannot remain in his role in Parliament. The issue is so egregious and so serious, it's completely untenable."
However Seymour said a byelection would only elect someone for four months.
"They wouldn't be elected for two months from now, then the winning candidate would have to immediately start campaigning for the general election in October.
"It hardly seems like, with all the challenges Napier faces right now, two elections in four months is the number one thing they need."
