National Party leader Christopher Luxon is not ruling out working with New Zealand First, after Winston Peters said Labour could not be trusted.
In a break with his usual approach, Peters has ruled out working with his former coalition partner, accusing it of deliberately withholding information about its work on He Puapua, and what he describes as its "separatist" agenda in other areas.
In past elections he has kept his options open, to give him and his party a stronger hand in post election negotiations.
"In the past we have worked with both Helen Clark and Jim Bolger. We shook hands with them and they both kept their word. So did we," Peters tweeted on Monday.
"In 2017 Labour shook hands with us then spent millions on the He Puapua report and other plans deliberately hidden from us.
"Lying to their coalition partner and going back on their word is the reason we will not go back into government with them.
"Nobody lies to me and gets a second chance."
When asked about coalition relations, Prime Minister and Labour leader Jacinda Ardern said she would not "rewrite history... because actually I was proud of what we did, I'm just going to stand by that principle".
"Lots of politicians say lots of things about one another," she replied when Peters' comment about Labour not being trusted was put to her.
Ardern was also asked if she would keep open the option of working with New Zealand First: "I'd like to think I've got now a history that demonstrates that I can work with a range of different people - and I stand by that", she said.
National's Christopher Luxon refused to be drawn on Peters' comments, but would not rule out a post election deal.
"Well look, way too early to speculate on any electoral calculations; as I've said, if you want to change this government, and a lot of New Zealanders do, there's only one thing to do and that's party vote National."
Former National Party leaders John Key and Simon Bridges both ruled out working with New Zealand First at various points along the way - would Luxon do the same?
"All I'm saying to you, is that the right way, if you want to change this government, is party vote National in 2023... that's all I'm gonna say to you."
New Zealand First has polled about 3 percent mark in recent surveys - to enter Parliament it would need to top 5 percent in the party vote or win an electorate seat.