The League of Conservation Voters is asking Rep. William Enyart (D-Ill.) to return a campaign contribution for backing a coal-friendly bill.
The green group's action fund donated $5,000 to Enyart's campaign in 2012 after he promised in a candidate questionnaire sent out by the group to defend the Clean Air Act if elected to Congress.
The bill ensures that "regulations are based on technology that is proven and commercially available for use," said Sen. Joe Manchin (D-W.Va.), co-author of the legislation with Rep. Ed Whitfield (R-Ky.).
In a letter to Enyart on Thursday, the League of Conservation Voters calls the bill "one of the broadest attacks on the environment we've seen yet from the Republican leadership."
"The reality is you are never going to agree with someone 100 percent of the time," Jeff Gohringer told The Hill.
"But this is about someone who went back on his word and co-sponsored legislation to gut the Clean Air Act and at the end day his words don't match his actions," Gohringer said.
Gohringer said this is the first time anyone can remember that the green group has asked for a contribution back.
"It's such an extreme step to co-sponsor a bill that does the exact opposite of what you said you were going to do," Gohringer added.
Enyart, who is up for reelection this year, has not responded to the letter.