AUGUSTA — The National Organization for Marriage, the nation’s leading opponent of gay marriage, has filed two retaliatory complaints claiming that its adversaries violated Maine election laws more than four years ago.

The complaints against the Human Rights Campaign and the National Gay and Lesbian Task Force stem from campaign activity in the 2009 referendum over Maine’s legislatively enacted gay-marriage law, which voters overturned. They are a direct response to a decision May 28 by Maine’s ethics commission to fine the organization a record $52,250 for failing to register as a ballot question committee and for keeping its donors and activities secret during the 2009 campaign.

Fred Sainz, a spokesman for the Human Rights Campaign, said the anti-gay-marriage group’s “nuisance complaint” further illustrates that it operated illegally while his organization followed disclosure laws.

John Eastman, board chairman for the National Organization for Marriage, promised to file complaints against his opponents immediately after the five-member Commission on Governmental Ethics and Election Practices accepted findings from a staff investigation that NOM violated Maine law.

Eastman said the investigation singled out his organization for activity that was also practiced by groups advocating for gay marriage. That argument, along with the counter-complaints, could play into NOM’s anticipated legal appeal of the fine and the requirement to disclose the names of its 2009 donors.

The appeal is likely destined for Maine Superior Court, but it cannot be filed until the ethics commission ratifies the investigation at its next scheduled meeting June 25. The vote taken May 28 was to accept the findings of the probe and the recommended fine. The vote in June will formalize the findings in writing and open a 30-day window to appeal.

The commission will hear the complaint against the two gay-marriage advocacy groups on July 31.

The complaint against the National Organization for Marriage was filed in 2009 by Fred Karger, a gay-rights activist from California who alleged that the organization effectively laundered its donations to a Maine-based ballot question committee – Stand for Marriage Maine – to conceal the identity of its donors.

The National Organization for Marriage alleges that two of its opponents used similar methods.

Karger’s complaint, and the two filed by NOM, center on the ability of tax-exempt nonprofit organizations to engage in political activity while shielding donors’ identities. Donations to so-called social welfare organizations are confidential, which has made the groups the preferred pass-throughs for individuals or organizations that want to influence elections but keep their activity secret.

Maine law says contributions over $5,000 to any organization specifically designed to influence an election must be disclosed. During the 2009 campaign, the National Organization for Marriage never filed as a ballot question committee, yet donated more than $2 million from its general treasury to bankroll the $3 million effort to overturn the gay-marriage law.

Brian Brown, the organization’s president, was an officer of the Maine-based PAC that led the campaign, a dual role that the ethics commission said allowed the organization to skirt Maine’s donor disclosure law.

The ethics commission staff used confidential tax records obtained through court discovery and fundraising appeals to show that the national organization solicited donations earmarked for the Maine referendum. The records show that some donors gave specific amounts to the national organization’s treasury, and that on the same day, identical or nearly identical amounts were transferred to Stand for Marriage Maine.

The Portland Press Herald has requested the names of the donors through a Freedom of Access Act request. The ethics commission denied the request, saying the information is shielded as sensitive financial information. The information will become public if the national organization complies with the commission’s ruling or if the ruling is upheld on appeal.

The National Organization for Marriage filed its counter-complaints on the day of the ethics commission’s ruling. In his requests for an investigation, Brown, the organization’s president, maintains that his organization did nothing illegal in 2009. His request to investigate his opponents, he wrote, is warranted only as the laws have “recently been interpreted and applied” by the commission.

The organization alleges in its complaint that the Human Rights Campaign made about $210,000 in transfers from its general treasury to Maine-based political action committees. Brown wrote that the group broke Maine law because the donations to the treasury were solicited in emails identifying the Maine referendum as a potential destination for the money.

“The source of these contributions was, therefore, never disclosed to the people of Maine, and Maine voters were deprived of information concerning who was spending money to influence their vote in the ballot question election of 2009,” Brown wrote in a passage that mirrored language in the ethics report on the National Organization for Marriage.

According to campaign finance records, the Human Rights Campaign filed as a ballot question committee in 2009 and spent more than $145,000 to fight the repeal of the gay-marriage law. The group and its associated ballot question committee also gave cash and in-kind contributions to No on 1 Protect Marriage Equality, the Maine-based PAC that led the campaign to defend the law.

Darrin Hurwitz, deputy legal counsel for the Human Rights Campaign, said the new complaint is vindictive and baseless. He said his organization created a PAC that raised and spent money on the referendum while disclosing that activity to the public.

Asked about the transfers from the group’s general treasury to the PAC, Hurwitz said treasury donations are never earmarked for a specific campaign and his group was in gay marriage battles all over the country.

The National Gay & Lesbian Task Force Foundation, a national nonprofit, moved about $140,000 from its general treasury to Maine-based PACs defending the marriage law. Brown argued that the foundation violated the law because it never registered as a ballot question committee or disclosed its donors.

“The task force is confident that we fully complied with Maine law. If the commission decides to take this complaint, we will respond accordingly with the information it may require,” Darlene Nipper, the foundation’s deputy executive director, said in an email.