Supporters of Ohio's gay marriage ban have filed a legal challenge to a petition seeking to repeal the ban.

Earlier this month, Ohio's Ballot Board cleared a proposed amendment filed by Freedom to Marry Ohio which would legalize gay marriage in the state. It would repeal a constitutional amendment defining marriage as a heterosexual union, which passed in 2004 with overwhelming support.

The group now must collect roughly 385,000 valid signatures from at least half of Ohio's 88 counties to get the proposal on next year's ballot.

The Ohio Campaign to Protect Marriage, the group behind the 2004 amendment, on Tuesday filed a lawsuit against Attorney General Mike DeWine, the Dayton Daily News reported.

The suit asks the Ohio Supreme Court to disqualify DeWine's approval of the proposed petition, arguing that the petition summary is invalid because “it is not a summary and is not a fair and truthful statement of the proposed constitutional amendment.”

Mary Jo Kilroy, CEO of Freedom to Marry Ohio, called the lawsuit “frivolous.”

“Although we have not seen the lawsuit, we are not surprised that there are opponents trying to stop the campaign,” Kilroy said in a statement. “We will continue to exercise our right to petition. We believe Ohio voters will support the proposed amendment which allows the freedom to marry while recognizing the rights of religious institutions.”

(Related: Tim Hagan walks away from effort to repeal Ohio gay marriage ban.)