The leaders of Labour and the Green parties are appearing together at Waitangi in a show of unity which they hope will draw a contrast with sparring coalition partners.
Neither opposition party were expected to unveil any new policy at the joint media conference at the Treaty Grounds today.
Earlier, Labour leader Chris Hipkins told RNZ's Morning Report programme it was intended to demonstrate an ability to cooperate sensibly in any future government.
"We want to send a really clear message that... you can work constructively with people, still have disagreements, without getting into abuse."
Hipkins said that was not the case within the coalition, pointing to New Zealand First leader Winston Peters' staunch opposition to the India free trade agreement.
"When you've got the Foreign Affairs Minister saying the Prime Minister's not telling the truth, I think that's an indictment on the current government."
Te Pāti Māori was not invited to take part in the media conference.
Hipkins told Morning Report the party still needed to sort itself out.
"They're in court. That's really where their focus should be."
Last year, Te Pāti Māori MP Mariameno Kapa-Kingi contested her expulsion from the party and was temporarily reinstalled in an interim judgement.
A substantive hearing is taking place at the High Court in Wellington.
