Iwi are uniting against the Government's Kermadec Marine Sanctuary just as they did against Labour's Foreshore and Seabed Bill.

The Maori Fisheries Trust is taking action against the Government in the High Court because it didn't consult them about removing Maori fishing rights in the area.

SEE ALSO: Govt faces iwi opposition to Kermadec sanctuary

The iwi organisations named in the Maori Fisheries Act have now pledged unanimous support for the legal action.

Chairman Jamie Tuuta said achieving a rare show of unity from iwi should send a strong message to the Government about its process.

"We're not happy about the Government decision on this matter, and the Government may need to rethink its approach and decision," he said.

Mr Tuuta said iwi ought to have been consulted, before their fishing rights in the area were revoked.

"That didn't occur, and discussions weren't that positively received by the crown, and so we had no other option but to pursue the legal pathway."