The announcement of the Trans Pacific Partnership (TPP) shows a complete lack of understanding of Treaty of Waitangi principles, a lawyer says.
The Waitangi Tribunal has granted a group of claimants challenging the deal an urgent hearing, which is expected to take place in January.
The trade ministers of 12 Pacific countries, including New Zealand, announced on Tuesday after a marathon series of talks that an agreement had been reached on the TPP.
The deal - if ratified - will see the loosening of a wide range of trade barriers, from drug patent protection and digital data protection to access to foreign dairy markets.
The claimants had asked the Crown not to take any steps that would undermine the claim before it could be heard by the tribunal, but it declined without giving any reasons.
The Federation of Māori Authorities has praised the agreement. But the lawyer representing the claimants, Kathy Ertell, said it was regrettable that the Crown had gone ahead without the support of its treaty partner.
"It shows a complete lack of understanding of what the principles of the treaty are, which are about the development of a relationship going into the future together between the Crown and Māori - not the Crown just rushing off and doing whatever it wants when it comes to making agreements which may compromise the sovereignty of New Zealand.
"It becomes even more important that the Crown takes its treaty partner into its confidence."
Ms Ertell said the Waitangi Tribunal hearing in January would be an opportunity to discuss trade issues affecting Māori with the Crown.