WASHINGTON - An environmental group that last year helped defeat conservative House Resources Committee Chairman Rep. Richard Pombo, R-Calif., is taking aim at five more Western Republicans over global warming.

The lawmakers from California, Arizona, Nevada and New Mexico have their "heads in the sand" about the dangers of climate change, the Defenders of Wildlife action fund charges in a radio and Internet ad campaign that began Thursday.

"We're looking to send a clear message that the American people won't tolerate representatives who continue to favor big polluters and their special interests," Defenders action fund president Rodger Schlickeisen said.

Schlickeisen said in an interview that all five lawmakers - Reps. John Doolittle and Ken Calvert of California, Rick Renzi of Arizona, Dean Heller of Nevada and Steve Pearce of New Mexico - have opposed measures that would rein in oil and gas development in the West and control greenhouse-gas producing pollution.

Several of the lawmakers pushed back Thursday. Heller accused Defenders of wanting to close down mining and public lands in Nevada and "take away our guns."

Heller said Defenders was "polluting the air waves" with their ads. "If we're going to talk about pollution let's talk about who's polluting here," he said.

Although all five lawmakers could face tough re-election bids in 2008, Schlickeisen insisted that the group just wants them to change their positions on global warming.

But the campaign is modeled on the tactics the groups used to defeat Pombo.

Pombo was a pro-energy chairman of the House Resources Committee who infuriated environmentalists. Defenders, the Sierra Club and others spent more than $1 million to defeat the seven-term incumbent at the peak of his power.

Environmentalists now are pressing for action on global warming, an issue that is popular with voters, particularly in the West.

Scientists have said the bone-dry Southwest is particularly vulnerable to the climate changing effects of global warming. The region also has seen increasingly frequent skirmishes over oil and gas drilling on sensitive wild lands.

The lawmakers defended their record on the environment.

Doolittle's chief of staff, Ron Rogers, said Doolittle was the lead author of the Lake Tahoe Restoration Act which invests $300 million for environmental restoration in the Lake Tahoe Basin.

Pearce in the past week has offered several amendments to a House energy bill in favor of clean fuel development, his spokesman Brian Phillips said.

Calvert said he supports finding solutions to climate change "in a way that does not overreact and punish the American economy" and that he has pushed for research and conservation.

"I understand that it is fundraising season for some environmental groups, but in my case they've got the wrong guy," Calvert said.

A spokesman for Renzi did not immediately respond to requests for comment.

Of the targeted lawmakers, two - Doolittle and Renzi - are the subjects of federal corruption investigations.

Questions have also been raised about Calvert, who pushed federal funding for a planned freeway interchange 16 miles from property he sold at a profit.

All three say they have done nothing wrong.