WASHINGTON, D. C. -- A secretive political action committee that spent hundreds of thousands of dollars to boost Jim Renacci's U.S. Senate campaign broke the law by waiting months to disclose its activities in May's Ohio primary, says a complaint filed at the Federal Election Commission.

The complaint says Ohio First PAC 's delayed disclosures not only violated federal law, "but also robbed Ohio Republican voters of the opportunity to know who was attempting to influence their votes before they cast those votes."

"Such a betrayal of the public trust should be investigated to maintain the integrity of our elections," the complaint filed by a labor-backed Democratic political action committee American Democracy Legal Fund says.

Federal Election Commission filings by Ohio First PAC indicate it spent more than $100,000 on media production and placement in the weeks leading up to the primary, and more than $150,000 on printing and postage. It also spent money on fundraising consulting and survey research. The organization has a pro-Renacci website at ohiofirstpac.com.

Disclosure forms that the group was supposed to filed at the Federal Election Commission before the May 8 primary, and within 24 and 48 hours of the incurred expenses, didn't show up until June 29, nearly two months after the election.

Ohio First PAC's most recent FEC filings show that it has raised $79,200 and accumulated nearly $600,000 in debts to vendors. Its large donors included two mining supply companies - Swanson Industries of West Virginia, which gave $30,000 and GMS Mine Repair and Maintenance Inc, of Maryland - which gave $10,000. It got $20,000 from Illinois Republican donor Richard Colburn, and $15,000 from the Ancora Group of Cleveland, a family wealth planning company.

Julie Dozier, the treasurer of the Ohio First PAC, did not respond to a request for comment sent to the email she listed in its paperwork. The organization says its address is a Virginia post office box.

An FEC spokesman said he couldn't comment on matters pending before the commission.

The former press spokesman for the campaign of Renacci's chief GOP Senate primary opponent, businessman Mike Gibbons, said he hadn't heard of the Ohio First group. Gibbons himself did not respond to an emailed request for comment.

Renacci's campaign is not legally allowed to coordinate with outside groups, and a campaign spokesperson declined comment on Ohio First PAC or the complaint filed against it.

American Democracy Legal Fund president Brad Woodhouse, a longtime Democratic Party activist, said there has been an explosion of secretive groups that make independent expenditures since the U.S. Supreme Court's 2010 Citizens United decision.

"That Renacci is relying on such a group for his long shot bid for the Senate isn't what is surprising," Woodhouse said in an email. "What is shocking is that they would so blatantly and serially and apparently purposefully violate federal election law."