Rep. Ed MarkeyEdward (Ed) John MarkeyDem calls for CDC to immediately begin gun violence research Historian Meacham: Bolton 'raises the stakes for military action around the world' Democrats lay into Trump's pick of Bolton for national security adviser MORE (D-Mass.) pledged to launch an immediate investigation Friday following the revelation that some groups opposed to climate change legislation forged letters by minority groups to mischaracterize those groups' stances.

"This fraud on Congress shows that some opponents of clean energy have resorted to forgery and theft to block progress," said Markey, the chairman of the House Select Committee on Energy Independence and Global Warming and principal author of "cap-and-trade" legislation in the House.

The Charlottesville Daily Progress reported Friday that freshman Rep. Tom Perriello's (D-Va.) office had received letters purportedly from Creciendo Juntos, a Hispanic-advocacy nonprofit group, opposing the controversial climate change bill, as well as the NAACP.

The groups decried the letters as forgeries, and said the letters mischaracterized their positions.

Markey said that his committee would immediately begin an investigation of the forgeries, and warned other lawmakers to be on the lookout for false letters.

"I encourage all Members of Congress to be on the lookout for other suspicious and illegal materials," he said.