ProgressOhio announced Monday that it had filed a complaint with the Federal Elections Commission, alleging that Murray Energy made an illegal corporate contribution to Mitt Romney’s presidential campaign.

Coal miners in Ohio said they feared being fired if they did not attend an August 14 event with the Republican presidential nominee. Images from the event are now being used in a pro-Romney ad.

"It is clear from published reports by executives at Murray Energy that employees were mandated to attend the August 14 Romney rally after closing the mine," said Brian Rothenberg, Executive Director of ProgressOhio. "Clearly the use of these miners in television ads is meant to convey something of value to the Romney campaign and is therefore a violation of federal law."

Rothenberg's complaint alleges the company violated federal campaign laws that prohibit a corporation from using the threat of a detrimental job action to force employees to make a contribution on behalf of a candidate.

Robert Murray, the founder of Murray Energy, is a major Romney supporter. Between 2005 and 2009, the Murray Energy Corp. Political Action Committee had given more than $150,000 to Republican candidates. Murray personally gave $15,000 to the National Republican Senatorial Committee in 2004 and $10,000 in 2006. The Ohio Valley Coal PAC, a group affiliated with Murray Energy, gave $10,000 to George W. Bush’s presidential campaign in 2000.

But the company denies any wrongdoing.

"It is readily apparent that the complaint is nonsensical and completely without any merit whatsoever," Murray Energy said in a statement. "It is clearly an attempt by ProgressOhio to try to embarrass the Romney campaign and to blunt and eliminate criticism of Mr. Obama’s War on Coal."

Watch Romney's ad, uploaded to YouTube, below: