The Maori Party warned at the time that its ongoing support depended on the Government's consultation with Maori and any plans to compensate affected iwi.
Co-leader Marama Fox reiterated today that its support for the bill was not guaranteed. The party was talking to iwi with interests in the Kermadecs before it determined its position.
"We supported the idea of a sanctuary," she said. "But the Government has been negligent in getting consent and getting consultation with all of the iwi involved."
The Act Party has also said that it could vote against the bill, on the grounds that the no-take reserve infringes on fishing rights without offering compensation.
If Labour, the Maori Party, and Act withdrew their support, National could still pass the bill with support from the Greens, United Future, and New Zealand First.
Labour and the Maori Party want Te Ohu Kaimoana's legal challenge to be resolved before the sanctuary is established.
Prime Minister John Key yesterday said that the Government intended to press on despite the court action. The sanctuary was expected to be in place by November.
The proposed reserve covers 15 per cent of New Zealand's exclusive economic zone and would include 39 species of sea birds, 35 species of whales and dolphins, three species of endangered turtles and 150 species of fish.
About 20 tonnes of fish, mostly tuna, is caught within the boundaries of the proposed reserve each year. The fishing take is worth about $250,000 but iwi say it would be worth much more if fully developed.
