Te Rūnanga o Makaawhio has come out against plans for a Haast to Hollyford road, a proposal that has been around for decades.
The rūnanga said it had sought feedback on the plan from its 3000 members; some were for but most were against.
Its tūmuaki, or general manager, Susan Wallace, said building a road to boost tourism would come at a cost.
She said her people were not convinced that the proposed benefits would outweigh the fact that the area was too special to open up.
"We think there need to be places that remain untouched and people shouldn't need to access every inch of our country by road.
"You get to experience an area that's so remote and so untouched it's like you're in a place by yourself".
Ms Wallace said the isolation of the area was a drawcard.
"The remoteness and the feeling of being alone in countryside that has scarcely known human contact already draws visitors to this area, with the popular Ngāi Tahu-owned Hollyford Track guided walks.
"It does not need a highway slashed through the middle of it. This is the last bastion of South Westland and as tangata whenua we will fight to keep it that way," she said.
The project is being promoted by a subsidiary of Westland District Council.