Whangaroa hapu and Treaty claimants have written to Treaty Negotiations Minister Chris Finlayson to reject the Tuhoronuku mandate and have accused the minister of trying to prop it up.
"We support police vetting for all members of any negotiation body or settlement entity," the letter says.
"And we continue to oppose Te Runanga-a-iwi o Ngapuhi being given any seats on the negotiation body."
The Whangaroa hapu support messages Mr Finlayson earlier received from Te Kotahitanga o Nga Hapu Ngapuhi, Hokianga hapu, Te Waimate Taiamai and Kaikohe hapu.
"We agree with the comments those groups have made and we share the concerns they have raised," the letter says.
Whangaroa hapu and claimants wish to have their claims heard by the Waitangi Tribunal in the second stage of its Te Paparahi o Te Raki inquiry.
"We of Whangaroa have been railroaded without out consent into having our lands, marae and hapu being included in the groups Tuhoronuku claims support it," the letter says.
"We remind you that you and your officials have been informed many times that Te Runanga-a-iwi o Ngapuhi and Tuhoronuku do not and cannot speak for or represent Whangaroa.
Mr Finlayson was asked to withdraw his proposals regarding the Tuhoronuku mandate and instead support the tribunal's stage 2 hearing to make it as well resourced and efficient as possible.
The letter to him was signed by 22 Whangaroa hapu representatives and Treaty claimants.