UPDATED: 2.52PM The Maori Party is threatening to withdraw its support for the Kermadec Ocean Sanctuary, if the Government and iwi can't reach an agreement.

The Government has said it will not bow in the face of continuing iwi pressure over its decision to create the marine sanctuary.

Maori Party co-leader Marama Fox said National is trying to force them to choose sides in the spat, which is typical divide and conquer tactics.

She said the Government is being too casual about honouring the Treaty, and needs to at least commit to a proper discussion with iwi.

"We supported the idea of a sanctuary, but actually the Government has been negligent in getting consent and getting consultation with all of the iwi involved."

Te Ohu Kaimoana, the Maori Fisheries Trust has rolled out senior figures from Maoridom to back its view the creation of the sanctuary extinguishes fishing rights gained in the 1992 Sealords settlement.

The Maori leaders, including Sir Tipene O'Regan, Dame Tariana Turia, and Sir Mark Solomon, aired their concerns at a media conference in Wellington yesterday.

Sir Tipene O'Regan said it completely undermines iwi fishing rights under Treaty of Waitangi settlements, and only two iwi were consulted.

"We've already provided for the Kermadecs to be protected, we've already made provisions, we've already developed a model," he said.

"Coming in here and pushing us around and pushing our political leaders around in the manner they have is reprehensible and it has to be opposed."

But the Prime Minister said the Government's position is clear -- fish that could be caught in the sanctuary are migrating species and can be caught outside of the Kermadecs.

"We don't think that there is an economic loss to Maori. We also think that Maori have been very strong advocates for conservation and for the preservation of both fisheries and other resources, and we believe we are doing that in the best interests of all New Zealanders."

Environment Minister Nick Smith said it's a business opportunity to brand, as consumers are starting to care more about sustainable fishing.

"There's far more gains for TOKM, for Maori, and for the commercial fishing in embracing the Kermadec Ocean Sanctuary and telling it as part of story as to why New Zealand fishing products are so valuable."