Prime Minister Jacinda Ardern will this morning sign a cooperation agreement with the Green Party that will give its two co-leaders ministerial portfolios outside of Cabinet.
Around 85 percent of roughly 150 Green delegates voted in favour of the deal on a lengthy conference call last night.
The delegates were presented the deal following several rounds of talks between Labour and Green leaders that concluded on Thursday.
The Greens went into the discussions with little to no leverage - and so no hope of a formal coalition - given Labour can govern alone.
'Tense' conference call
RNZ has been told by people on the call it was "tense" and delegates were nervous about what the proposed agreement would contain.
Delegates learned the contents and nature of the agreement at the same time Prime Minister Jacinda Ardern made it public yesterday afternoon.
After viewing the deal, some delegates were concerned it offered the Green Party very little, sources have told RNZ.
Some thought it would be better for the party to spend the next three years on the opposition benches, challenging the Labour government, they said.
Two hours into the conference call, some delegates indicated they would block consensus and force the decision to a vote, RNZ understands.
The party is required to make most decisions by consensus, but if that's not possible a vote is taken and 75 percent support is needed for the motion to pass.
RNZ has been told by some on the call Green Party staff spent very little time trying to address the concerns of delegates wanting to block the vote.
They said this was unlike discussions after the previous election when delegates were considering a confidence and supply agreement with Labour.
Staff spent hours trying to smooth over and address people's concerns in 2017, sources said.
The party's acceptance of the deal means James Shaw will remain as the minister of climate change, but will also pick up associate environment with a focus on biodiversity.
Marama Davidson will take on the new prevention of family and sexual violence portfolio and will continue the work led by her Green Party colleague Jan Logie in the previous government.
Davidson will also become an associate housing minister and will largely work on addressing homelessness.
Labour will also support the nomination of a Green MP to be the chair of a select committee, as well as a Green MP in the deputy chair role of another one.
RNZ understands those select committees will likely be Environment and Transport and the roles will be filled by Eugenie Sage and Julie Anne Genter respectively.
The cooperation agreement means the Green Party can't oppose the government on confidence and supply matters, but can take their own position on other issues.
Areas of cooperation
The deal will also see both parties commit to three "areas of cooperation" but the goals are backed up with very little policy detail.
Firstly, the parties have pledged to achieve the "purpose and goals of the Zero Carbon Act" by decarbonising public transport and the public sector, boost the uptake of zero-emission vehicles and introduce clean car standards, as well as supporting the use of renewable energy for industrial heat.
Labour and the Greens are promising to protect the environment and biodiversity as part of its second area of cooperation, by working to implement the Te Mana o te Taiao - Aotearoa New Zealand Biodiversity Strategy 2020, protect kauri, work on pest management programmes and further minimise waste and "problem" plastic.
The final area is improving child well-being and marginalised communities. The parties say they will take action together on homelessness, warmer homes and youth mental health.
The leaders of both parties will meet every six weeks to monitor progress on the shared goals.
Ardern and the Green Party co-leaders will sign the cooperation agreement this morning in the Beehive.
The prime minister will unveil her Cabinet line-up tomorrow and ministers will be sworn in on Friday.
Environmental Defence Society spokesperson Gary Taylor said Shaw's portfolios were a big job for someone outside of Cabinet and he hoped Labour would back the minister's work.
"I think the big challenge now that James has been given with this appointment outside of Cabinet is for the rest of the Labour Cabinet to support him," he said. "Because both of those issues, climate change and biodiversity, are going to require a whole of government response."
Taylor said he expects to see moves made towards 100 percent renewable energy and the roll-out of electric vehicles fast-tracked.