The Ngapuhi runanga has thrown its support behind the Northland hapu, Ngati Hau, which has told an Australian mining company to stay out of its tribal territory.
De Grey Mining hopes to start test-drilling next month for gold and silver in the Puhipuhi hills north of Whangarei.
However, hapu elders have written to the company telling it to surrender its exploration permits.
Te Runanga a Iwi o Ngapuhi chairperson, Sonny Tau, supports Ngati Hau because mercury was once mined next to the proposed site.
He says there's a risk mercury could contaminate local waterways, including drinking water sources.
Mr Tau says the runanga isn't against mining as long as it doesn't harm the environment.