The Green Party has ratified the confidence and supply agreement with Labour, paving the way for a new Government to be formed with Labour, New Zealand First and the Greens.
Party leader James Shaw told media late tonight that the party delegates voted in favour of the agreement - with about three delegates opposing the agreement.
"The Green Party has decided overwhelmingly to support the confidence and supply arrangement that we negotiated with the Labour Party ... We're all in, and there will now be a new Government led by the Labour Party and by Prime Minister Jacinda Ardern.
"There were about three votes against and about 140-something for ... there were a couple of people that had dissenting opinions and for actually quite good reasons, and we had a pretty robust and extensive debate about it, and then we made a decision."
He declined to elaborate on what the dissenting opinions were about.
The party had to have the approval of the party delegates to approve the confidence and supply agreement, according to the party's constitution. Without consensus, the motion had to go to a vote, with at least 75 per cent support to move forward.
A Labour-led Government would be a historic moment for the Green Party, giving the Greens ministerial control over the issues that it deemed most important, Greens leader James Shaw said late today.
While Shaw did not disclose many policy details in the arrangement, he said it included three ministerial positions outside Cabinet, and one undersecretary role.
"This is a historic moment for the Green Party and for our movement because, for the first time, we are going to be, probably, in a position to have ministerial control in the areas that are important to us and the areas that we campaigned on.
"We are very excited about this opportunity."
Shaw was "very confident" the agreement would be approved by the Green delegates, given that that party had campaigned on changing the government, and they were now in a position to be able to do so.
He said the agreement should be made public in the coming days, and no decision had been made yet about which Green MPs would take portfolio positions.
"I wanted to give the Prime Minister some time for her to put together a Cabinet before we release that."
Shaw had previously said he preferred to be in coalition, but he was not disappointed the Greens would not be in Cabinet as the party would sit in on discussions on areas relevant to the party's portfolios.
"Also, we have the ability to retain our distinctiveness ... and I think that will be important for us in this very first time that we will be in government.
"Where we've landed up we think is a really good place for us to be."
The arrangement was a "rare and beautiful thing" because all parties would have to agree to pass any legislation.
"We are forced to find what we have in common, rather than what distinguishes us from each other."
While he was tight-lipped on policy gains in the agreement, Shaw stressed three campaign priorities for the Greens: be a world leader on climate change, restore and replenish forests, birds and rivers, and end child poverty.
He praised Jacinda Ardern and Labour for the parallel negotiations they ran with NZ First and the Greens. Parties obviously had differences that they campaigned on, but now they had to see what they had in common. It was the time to let bygones be bygones "... for the sake of the country".
He also thanked Bill English and the National Party caucus for their long service to New Zealand.