Alaska angered environmental groups this week after suing the US government over the listing of the polar bear as an endangered species.

The state filed suit against secretary Dick Kempthorne of the Department of the Interior asking for the bear to be removed from the list. The decision was not made on the best scientific evidence available, and the worldwide bear population has doubled in 40 years, it asserts.

The bear was put on the list after a long battle between conservation groups and the department, which ended with a decision in May. Although there were caveats in the decision designed to ensure development in Alaska is not unduly hindered, the state's governor Sarah Palin still registered her opposition to the move.

"This lawsuit and [Palin's] head-in the sand approach to global warming only helps oil companies, certainly not Alaska or the polar bear," retorted Kassie Siegel, climate, air, and energy programme director for the Center for Biological Diversity, this week.

Alaska's rationale for the lawsuit specifically mentions oil and gas exploration as financially important activities. Treating the bear as endangered could make it more difficult to carry out oil exploration and drilling plans in the region, it argues.

Last month, outgoing president George Bush urged Congress to lift a ban on offshore oil drilling that includes an edict on Alaskan waters. Last year, the Department of the Interior unveiled a plan for offshore drilling that encompassed eight Alaskan fields.