The largest U.S. nuclear power plant operator, Exelon, said it would withdraw from the U.S. Chamber of Commerce to protest its stand on global warming.

The move is not an isolated incident. The national chamber, which has more than 3 million members, has seen a few defections lately over its stance on climate change, The New York Times reported Tuesday.

The chamber opposes an Environmental Protection Agency proposal to set limits on harmful greenhouse gases, which would likely be used if Congress failed to act on a new climate change law, the Times said.

Pacific Gas & Electric in California and PNM Resources, which owns the largest utility in New Mexico, have also said they would drop out of the U.S. Chamber of Commerce.

"There will be significant vibrations from this. It's a bit of an earthquake," said Rep. Jay Inslee, D-Wash., a member of the Energy and Commerce Committee.

Exelon's Chief Executive Officer John Rowe said, "the carbon-based free lunch is over. Breakthroughs on climate change and improving our society's energy efficiency are within reach," he said.

The Chamber's Chief Operating Officer David Chavern said, "We just think the EPA is the wrong venue to be dealing with climate change issues."