Labour leader Phil Goff will be asked to explain his controversial "nationhood" speech at next week's party caucus meeting.
Discontent, especially on the Left of the party, has centred around Mr Goff's comments on the foreshore and seabed policy.
Insiders say the speech was discussed during a "robust" national council meeting of the party last weekend. The speech endorsed the current law but failed to reiterate the party's backing for a change that would accept the rights of iwi to seek customary title.
Mr Goff was criticised as "playing the race card" by Maori Party MPs, which he has denied.
Members of Labour's Maori caucus were absent when the speech was discussed in advance, and yesterday questioned whether they were given enough time to comment before it was delivered at a Palmerston North Grey Power meeting.
But a spokesman for Mr Goff said senior Maori MPs Parekura Horomia and Shane Jones were consulted and gave feedback.
Labour sources said Wellington Central MP Grant Robertson questioned the speech at last week's caucus meeting. He was again expected to be prominent among those expressing concerns at next Tuesday's caucus meeting.
Mr Robertson declined to comment yesterday. In a written statement, he said: "I believe these are important issues for New Zealand, and the country needs to be able to have a mature debate about them."
Sources said the party's ruling council had already asked Mr Goff to explain the speech on Saturday .
"There will be questions at caucus on Tuesday," one senior MP said.
But another discounted a move against Mr Goff's leadership, saying the concern should not be read as a sign of "deep divisions" in the party.
Mr Goff's spokesman said the matters raised in the speech were canvassed with the caucus before it was delivered. "Phil will be including the speech in his report to caucus along with all other current issues, so he is expecting it will be discussed again."
Mr Goff continued his attacks yesterday on National's deal with the Maori Party over the emissions trading scheme, which gave extra compensation to five iwi who said the value of their Treaty settlements would be hit by the scheme.
Labour has said the deal reopens settlements that were made as "full and final" in the 1990s. But he steered clear of the foreshore and seabed issue.
He attacked National's spending on the 2025 Task Force, led by former National leader Don Brash, which issued its report this week.
He said the task force had a budget of $477,000, of which $330,000 was yet to be spent, but the Government had said it would not be implementing the report's key recommendations so the rest should be spent "on something worthwhile".
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