The operator of the Ranger uranium mine in the Kakadu National Park says the proposed resources profits tax will make it less competitive internationally.

The chief executive of Energy Resources of Australia, Rob Atkinson, says the company is still trying to figure out the exact impact of the tax, but expects returns to be substantially lower.

Mr Atkinson says the tax is unfair, especially since ERA always reinvests a part of its profits.

"We've taken significant investment plus significant risk to get to this position and you do feel as though that it is unfair," he said.

"We believe we play and pay a very significant role both in the Territory and the community now with what we pay already."