AUGUSTA, Maine (AP) – A gay rights advocacy group claims that the Roman Catholic Diocese of Maine is violating tax rules by helping a referendum campaign that would repeal the state’s new same-sex marriage law.

The Empowering Spirits Foundation said its challenge was filed May 20 at an Internal Revenue Service office in Dallas. The San Diego-based group said the diocese is engaging in political activity by collecting signatures for the referendum, violating IRS rules applying to nonprofits.

The ballot question would overturn Maine’s same-sex marriage law. Same-sex marriage foes need the signatures of at least 55,087 registered voters to get the question on the ballot. The petitioners have until three months after the Legislature adjourns, which is expected to happen in mid-June, to collect the signatures.

IRS policy allows the diocese to participate in the campaign and help collect signatures, said Marc Mutty, public affairs director for the diocese. He rejected the IRS challenge as a “bogus attempt to sidetrack the campaign.”

Leonard Cole, a Portland attorney who specializes in tax and nonprofit issues, suggested that the church’s involvement could put it at odds with IRS rules that restrict lobbying by tax-exempt nonprofits.

“It’s hard for me to imagine how you seek someone’s signature on a petition without it arguably at least being an attempt to influence their vote once the measure was on the ballot,” Cole said.

Meanwhile, about a dozen same-sex-marriage supporters gathered in a park across the street from Maine’s Capitol to thank the Legislature for enacting the bill and Gov. John Baldacci for signing it earlier this month. The gathering also marked the start of the supporters’ campaign to defeat the referendum.

One of the participants, Carla Hopkins of Mount Vernon, said she was not discouraged that a same-sex marriage bill in New Hampshire has been set back by a House vote. Efforts are under way to negotiate a compromise acceptable to Gov. John Lynch.

“We’re riding high on what’s happening here in Maine,” said Hopkins, adding that she hopes to see similar laws passed throughout New England.

Four other states, Connecticut, Iowa, Massachusetts and Vermont, allow same-sex marriage.