The Chief Crown Negotiator is being accused of acting in bad faith in dealing with Treaty settlements.
Rick Barker is in charge of negotiating and concluding settlements on behalf of the Crown.
But one iwi - which is nearing the final stage of its Treaty settlement - has made a formal complaint against him to the Treaty Negotiations Minister, Andrew Little.
Mr Barker was made Chief Crown Negotiator in 2012 under the former Treaty negotiations minister, Chris Finlayson, and tasked with the job of negotiating and concluding settlements among iwi.
Auckland Hauraki iwi Ngāti Pāoa is frustrated at the way he has handled its settlement.
The iwi, which has interests in Auckland and around 3500 members, has initialled its individual iwi settlement with the Crown, but is concerned assets it believes should be included in the redress have been left out.
That includes a 2000 acre farm on Waiheke Island.
Ngāti Pāoa Iwi Trust chair Gary Thompson said Mr Barker was rushing the settlement process.
"Before we can sign off on any of our settlement agreement, we want some clarity around a couple of issues and our push to have that clarity is not in Mr Barker's best interest.
"We perceive that he's in the background manipulating things to be able to get the settlement over the line, ahead of our comfort."
At a recent iwi hui, Ngāti Pāoa voted unanimously to make a formal complaint against Mr Barker.
"They're telling us to jump to their tune before they give anything back, that's not good faith, and we have to complain. It impedes our ability to achieve a full and final settlement,"
Ngāti Pāoa are also part of the Pare Hauraki Collective, a group whose settlement was at the centre of protest this year.
Several iwi across the North Island oppose the settlement because of their overlapping interests.
Ngāti Pāoa iwi member Lucy Tukua said she believed Mr Barker and the Crown were responsible for pitting iwi against iwi.
In a statement she said her people had had enough.
"Our people will not be bullied. Mr Barker's behaviour wreaks of paternalism at best, and downright manipulation at worst.
"Our people are familiar with this tactic of divide and conquer and we will not put up with it."
Mr Barker has declined to comment.
Ngāti Pāoa kaiārahi Hayden Solomon said the iwi had more interests in Auckland than any other iwi within its collective.
He said the best outcome from the formal complaint would be for the Crown to acknowledge that.
"What we're hoping for is redress that recognises the interests of Ngāti Pāoa in Auckland, nothing more and nothing less.
"We hold the largest majority interest in Auckland in the Hauraki grouping and the iwi wants to see a settlement that reflects that."
Treaty Negotiations Minister Andrew Little said he was taking the complaint seriously and had referred it to the Office of Treaty Settlements.
"When an iwi has very difficult circumstances in dealing with the Crown, tensions can rise in engagements between people, misunderstandings can emerge, and people can feel as if they have been slighted, or haven't been understood, or have not necessarily been respected."