Labour expects the Government to consult with it over a constitutional review to consider such issues as Maori representation, leader Phil Goff says.
The review was part of the National-Maori Party supply and confidence agreement and a paper on it has been considered by Cabinet at least twice.
Mr Goff said constitutional issues should be decided on a non-partisan basis but the Government had made no effort to contact his party over the review.
"The Government, I presume, will make an approach to try to get a cross-party agreement on something as fundamental as constitutional change in New Zealand," he said.
"I think the whole process should be inclusive, and that includes talking to all the parties across Parliament."
Prime Minister John Key said the Government had not yet decided when it would consult other parties.
"That's something we're going to have to consider, not just Labour but other political parties," he said.
"You'll remember that its genesis came from the confidence and supply agreement with the Maori Party so that's been our initial body of consultation ... between National and the Maori Party."
However, the nature of the review meant it was likely other parties would be consulted.