Two Yukon First Nations and two conservation groups are suing the territorial government over its plan to open a vast region of the Canadian North to development.
The groups say the Yukon government's land-use plan for the Peel River watershed violates land claims signed with aboriginal bands.
Lawyer Thomas Berger says the development scheme unilaterally ignores another plan seven years in the making that was supported by First Nations
The lawsuit will be filed this afternoon in Yukon Supreme Court by the Nacho Nyak Dun, the Tr'ondek Hwech'in, the Canadian Parks and Wilderness Society Yukon and the Yukon Conservation Society.
The 67,500 square kilometre watershed, that covers a large section of northeastern Yukon, was to have 55 per cent of the land protected under the original land use plan.
Instead, the groups say the government plan would open more than 71 per cent of the area to industrial development.