Representative Henry Waxman, the top Democrat on the House Energy and Commerce Committee, and Senator Sheldon Whitehouse criticized EPA's April 30 decision to deny environmental law firm EarthJustice's petition for the regulation.

Waxman and Whitehouse sent an open letter to acting EPA administrator Bob Perciasepe on Tuesday, urging him to reconsider.

“The threat of climate change is so large and the window for action is so narrow that we do not have the luxury of ignoring any significant source of emissions,” the lawmakers wrote.

The pair criticised Perciasepe’s letter to EarthJustice in which the EPA top-dog wrote that “the agency must prioritise its regulatory actions” because it faces “limited resources and ongoing budget uncertainties” and that acting to reduce methane emissions from coal mines would “likely require significant agency time and resources.”

Waxman and Whitehouse said they understand budgets are tight but the answer cannot be to ignore a “major source of pollution causing climate change”

They gave Perciasepe back his own EPA statistics, which state that coal mines are the fourth biggest source of methane emissions in the United States, and according to the World Resources Institute, can be reduced by 24% at a cost of $5 per tonne.

The pair have consistently pushed Obama to pull administrative levers on climate issues and in the letter, alluded to a Congressional failure to act on climate change and urged federal agencies to step in.

“In these circumstances, your first responsibility should be to assess the risk and alert the public,” Waxman and Whitehouse wrote.

“If the risk is a significant one that you cannot find the resources to address, you should at least inform the President and Congress and appeal for additional resources.”

They concluded by saying Perciasepe’s current decision, “does not meet the President’s standards” and urged him to reconsider.