Waikato-Tainui says Tukoroirangi Morgan is no longer the head of the tribal executive.
An election of officers, including the chair of Te Arataura and the tribal parliament, was held in Hopuhopu near Ngaruawaahia on Sunday.
In a statement issued by the tribe, it said nine of 10 members were voted on to the executive during the Triennial Special General Meeting and Mr Morgan missed out.
The statement said a meeting to decide the final member will be held at a later date.
An iwi spokesperson told Te Manu Korihi that the new head of Te Arataura will be elected at the executive's first meeting.
Tukoroirangi Morgan says he plans to challenge the election results and will file legal action on Monday.
Mr Morgan believes he secured enough votes to continue as chair of the executive.