Winston Peters has fired a shot at the Greens' relevance to coalition negotiations, suggesting the party plays a minor role in any final decisions.

The New Zealand First leader said regular reports of a "Labour-Green government" over the past three years were wrong.

Leaving this afternoon's meeting with Labour, Peters said the meeting went "very well", with both sides working through the assigned material faster than expected.

Asked about James Shaw's comment earlier today that he trusts Jacinda Ardern to strike a fair deal with the Greens, while negotiating a separate deal with NZ First, Peters said he couldn't speak for Shaw.

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"Contrary to what you people say, I've never had a bad word with him or about him, that you could possibly quote. Because I've never said something bad about him in my career.

"So could you just leave it at the fact that I'm talking about New Zealand First and what we are doing, rather than any other party."

Discussions were still all about policy, Peters said.

"It will be policy all the way up to tomorrow night."

Peters was unimpressed when asked his verdict on some home baking apparently taken by Ardern into the meeting.

"This is a rather serious issue, alright? It is about the next Government of this country and you ask me about a cake? Why have do you always have to drag things down to a pit like that."

Ardern said good progress was being made.

"We are making excellent progress still, working through a number of policies which are important both to New Zealand First and to the Labour Party.

"Looking forward to holding another meeting this evening. Again, to continue talking about the policy priorities and how we can move forward New Zealand both economically and socially."

NZ First will meet again with National at 4pm, and Labour at 6.30pm.

Peters won't meet with the Greens and has said he doesn't want Labour to update NZ First on what the Greens want. Greens leader James Shaw says he trusts Ardern to work out a deal that his party will be happy with.

At least 75 per cent of Green party members will need to approve any deal, and this will be done through delegates.

Asked if he was concerned about that process, Peters implied the sign-off process wouldn't be complex because of the number of delegates that would be consulted.

"You should know far more about the Greens than I do. But they don't have to go back to their membership. They have to go back to about 170 members. Even I know that."

Peters turned on a journalist who asked about how the Greens would fit into any deal.

"For two years you have run a Labour-Greens Government. Now you are asking me why you made that mistake for two years...you got it all wrong.

"Please don't ask me to explain your gross misrepresentation of the political situation in this country for the last three years."