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Former leader Simon Bridges in February announced a decision by his MPs that the party wouldn't work with NZ First to form a government after the September 19 election.
When Todd Muller took over as National leader he said it was possible that the decision could be revisited in future, and he'd make clear the final decision before the campaign.
But Collins has slammed the door shut on the chances of reversing the decision not to work with NZ First.
"We have made that very plain as a caucus and as a party, and I know a lot of our party supporters and voters certainly wanted us to do that," she said today.
"I'm pretty clear - the caucus has decided it. That's the caucus view."
The National leader spoke to media after putting up new campaign billboards in her Papakura electorate, joking that the electric drill reminded her of holding a Taser.
NZ First is holding its annual conference in Auckland today and tomorrow.
Collins said she had a cordial relationship with Peters - "he's always pleasant with me, and I'm always pleasant to him" - but that didn't mean they could be in government together.
"This is not likely, because I don't know his party's going to be there after the election.
"It's really important to understand the caucus has said that they don't want to do a deal with Winston Peters. There is no reason that I know that we are going to change that.
"My view is I'm just not worried about him, or his party vote. I'm focused on the National Party vote."