Whanganui River Maori Trust Board is rejecting an accusation of not keeping tribes up-to-date with progress on a Treaty of Waitangi deed of settlement relating to the waterway.
Ngati Uenuku is critical of the way the board is handling the matter, saying it fears its rights are not being fairly represented.
The deed will establish the Whanganui River as its own legal entity, to be managed by iwi.
Ngati Uenuku says the trust has not properly consulted its iwi, it hasn't seen the document and it has no tribal representation on the mandating body.
But, the trust's negotiating team says no one has been left out of discussions; most recently, face-to-face talks with various Ngati Uenuku entities have been held since December.
None of the iwi have seen details of the deed of settlement because that's still being concluded in negotiations with the Government, the trust says.
The negotiating team plans to provide details of the draft document to its people once the deed is initialled at Parliament on Wednesday.
It says a three-week period will be available for discussions on aspects of the entire deed of settlement, and post-settlement governance arrangements before the deed is formally voted on by iwi members.