National Party leader Simon Bridges says his caucus is united behind his decision to rule out working with New Zealand First after the election.
Yesterday, the Opposition leader ruled out working with New Zealand First in any potential government after this year's election.
In response, New Zealand First leader Winston Peters said he was "unfazed", and suggested that if National needed New Zealand First and Bridges didn't call him then another member of the National caucus would.
Bridges told Morning Report it was his call to rule out the party, but he did consult with colleagues and signalled his intentions to his caucus and the board, all of which he felt were in unanimous support.
"It's not just me as I say, it's a view my caucus shares, a view that the board that I also met with before announcing the decision shares and endorsed.
"We're ruling out New Zealand First, full stop. If they hold the balance of power after the next election, we're not working with them."
Asked if this would also include other options such as a limited supply and confidence deal, Bridges insisted any formal arrangements with the party were ruled out.
"I don't see us doing any of those things.
"We're not doing what the New Zealand First has suggested, we won't be picking up the phone, we won't be seeking to work with them in any shape or form.
"And I think what's important about that are the reasons, I can't trust them and I don't think New Zealanders can."
He said he wanted to give voters a clear sense of certainty and choice between National and Labour, Greens, and New Zealand First.
"It is pretty simple, if you want a National government, you have to vote for it, if you want a Labour, Greens, New Zealand First government, you have to vote for that as well, it's not for me to tell New Zealanders but I am making that certainty and choice quite clear."
While Bridges said he wanted to collaborate with others and believed in the MMP (Mixed-member proportional) system, he did not trust New Zealand First considering Winston Peters' lawsuit actions against MPs and staffers.
"I think that tells us prospectively for the future that it's about New Zealand First and not the interest of New Zealanders.
"I've used the word charade, what I mean by that is holding the country to ransom for weeks in quite a precious way, backroom deals throughout government, exceptional to any other MMP governments we've seen, whether it's waka jumping, oil and gas, or a bunch of other decisions."
The decision echoes one made by former National leader John Key in the lead up to the 2008 election, ultimately resulting in Peters' ejection from Parliament.
Speaking to Morning Report, Prime Minister Jacinda Ardern said it was up to voters to decide which parties would end up having to work together to form a government.
"In an MMP environment, I think ultimately people decide that and we then work with what democracy produces.
"We [Labour] can work with New Zealand First, and we can work with the Greens, and not just that we can form a stable solid government as we have for the last two years, the rest is for voters."