Prime Minister John Key faces a showdown with Maori Party co-leader Pita Sharples as the row over water rights threatens their support agreement.
Mr Key's comment that the Government doesn't have to consider Waitangi Tribunal recommendations has enraged the Maori Party.
Dr Sharples and co-leader Tariana Turia say it's an insult and they won't tolerate any undermining of the tribunal's mana.
"We view very seriously the comments by the prime minister that `we could choose to ignore what findings they [the tribunal] might have'," they said in a joint statement last night.
"It is of utmost concern in so far as it threatens the very heart of the Treaty of Waitangi relationship."
Dr Sharples says he will "most definitely" meet Mr Key to express his concerns.
The Maori Party signed a support agreement with the Government after last year's election.
Asked by reporters whether it was under threat he replied "not yet".
The escalating row over water rights is the result of the Maori Council lodging an application with the Waitangi Tribunal, seeking a finding that the partial privatisation of four state-owned energy companies should be put on hold until Maori claims to water ownership are resolved.
The tribunal will open its third day of hearings today and Mr Key has been pointing out its recommendations aren't binding on the Government.
He says the Government will "obviously look at" the recommendation that emerges in about four weeks but he hasn't left anyone in doubt over what he thinks about water ownership.
"The Government is very firm - no one owns water, we certainly don't believe Maori own water," he said.
The Maori Party strongly opposes the sale of 49 percent of the shares in Mighty River Power, Genesis Energy, Meridian Energy and coal miner Solid Energy.
NZN