John Key says he would sack Judith Collins if it turns out she really did try to go behind his back to gain support from Winston Peters.

But Mr Key is adamant Mr Peters' accusation that Ms Collins plotted against the Prime Minister aren't true.

The New Zealand First leader says last year a group from Team Collins approached him to see if he would work with Ms Collins as leader after the election.

"Her team was really working pretty hard behind the scenes to set it up to be the leader after the election and they wanted to ensure that they could go on being the government in that situation as well," Mr Peters said.

Ms Collins says Mr Peters is lying.

"I have never approached Mr Peters and I've never asked anyone else to do so on my behalf. And he is absolutely wrong. He would be the last person in the world I'd ever approach for anything," Ms Collins said.

Mr Key, when asked does he trust Mr Peters, said: "Ah in general, I think the government could potentially, or National could potentially work with him."

Voters not happy

But voters don't want Mr Key working with Ms Collins anymore, according the latest ONE News Colmar Brunton poll.

Asked if she should be stood down or resign as a minister over the release of a public sector employee's details to blogger Cameron Slater, 61% of voters said "yes" and 26% said "no".