Eminent historian Dame Anne Salmond has criticised the Waitangi Tribunal over its handling of the Ngapuhi sovereignty inquiry.
She says she is concerned about the growing legalism of the tribunal's processes and has declined to answer written questions and answers unless directed to do so.
The professor gave evidence last month supporting Ngapuhi's claim that its chiefs did not cede sovereignty to the Crown when they signed the Treaty of Waitangi.
The Crown has since called other expert witnesses who have disagreed with Dame Anne's view, and has asked her to reply to written questions arising from their evidence.
In her response, Dame Anne says the tribunal was intended to be a people's forum, but her evidence was curtailed by questions from a long line-up of lawyers, turning the tribunal and hapu into spectators.
She says commissioning witnesses late in the process, as the Crown has done, without any right of reply creates an imbalance and appears to subvert the search for truth.