An executive with Penn National Gaming, a company fighting Maryland’s expanded gambling plan, has taken responsibility for paying for an anti-gambling mailer sent out this summer by a gay-rights group, according to a state senator.

Sen. C. Anthony Muse (D-Prince George’s). (Photo courtesy C. Anthony Muse)

The mailer, sent to Maryland households in August, asked residents to urge their representatives in the General Assembly to vote “no” on the gambling bill, which was the subject of a special legislative session. Next month, voters will get the final say on the legislation that passed.

The plan would authorize a new casino in Prince George’s County, as well as Las Vegas-style table games at the state’s existing five slots sites.

The mailer argued that the legalization of same-sex marriage, which is also on the ballot next month, stood a better chance of passage without the “complications” of a referendum on gambling appearing as well.

At the time, the Task Force declined to disclose the source of the funds for the mailer, which it later said cost $343,125.

On Thursday, Muse, who opposes the ballot measure, said that Snyder told him Penn had given money for the mailer to the DCI Group, a Washington-based consulting group, which in turn gave funds to the Task Force for the mailer.

Neither Penn nor the Task Force responded to several phone calls and e-mailed requests seeking comment on Thursday and Friday.

While such a funding arrangement does not appear to be illegal, Muse said he was troubled by the lack of disclosure. The state’s ethics laws need to be strengthened, he said.

“The public has a right to know,” said Muse, who represents the district that would be home to a Prince George’s casino and is also a minister. “It didn’t happen.”

An ethics form due several weeks after the legislative session required companies who employed lobbyists during the session to disclose spending on any outside groups.

Penn disclosed giving more than $1 million to the DCI Group. At the time, Karen Bailey, a Penn spokeswoman, declined to detail what DCI did with the money.

DCI did not hire lobbyists in Maryland during the special session and was under no obligation to disclose its spending.

Since the session, Penn has spent more than $18 million in a bid to defeat the expanded gambling measure in November — more than any party on either side.

Penn owns Rosecroft Raceway, a Prince George’s racetrack that would be eligible to bid for a casino license if the expansion plan passes. But Penn officials argue that the deck is stacked against them, because Prince George’s County Executive Rushern L. Baker III (D) and others have championed National Harbor as a better casino site.

Penn also owns a casino in Charles Town, W.Va., that analysts say would take a significant hit if another large-scale venue opens in Maryland. Proponents of the measure have accused Penn of acting to protect its interests in Charles Town.

The company also owns a smaller casino in northeastern Maryland which stands to benefit from table games if the ballot measure passes.