Developer Milt Peterson stands at the site where he wants to build a high-end casino at National Harbor in Prince George’s County. (Photo by ASTRID RIECKEN For The Washington Post)

Casino companies and other gambling interests dominate a new list of the top spenders on lobbying services in Maryland during the past year.

The list, compiled by the State Ethics Commission, captures the millions that were spent trying to influence the General Assembly — both in person and over the airwaves — as it crafted an expanded gambling plan that was put to voters in November.

The plan, which the public approved, allows a new casino in Prince George’s County as well as table games, such as blackjack and roulette, at Maryland’s existing slots locations.

A group called Maryland Workers for National Harbor tops the list, with reported spending of more than $2.7 million to persuade lawmakers to enact the gambling plan. Much of that was spent on radio and television ads in advance of a special session in August. (Money spent on the subsequent multi-million ballot-issue campaign targeting voters is not included in the tally.)

Funders of the workers group included the Peterson Cos., the developer of National Harbor, the 300-acre mini-city on the Potomac River that is widely considered the leading site for a Prince George’s casino.

Penn National Gaming, which opposed the expansion plan, was also among the biggest spenders on lobbying services. Penn reported spending more than $913,000 during the reporting period, which ran from November 2011 through October 2012.

The Taxpayers Protection Alliance, a national group that ran television and radio ads opposing the special session, reported spending more than $755,000. The group did not disclose the source of its funds for its Maryland activities.

Another opponent of the plan, PPE Casino Resorts Maryland, reported spending more than $568,000 on lobbying. The company is a spinoff of the Cordish Cos. and owns Maryland Live!, the state’s largest existing casino, located in Anne Arundel County.

Other interests that made the Top 10 on the list include the Human Rights Campaign, a national gay-rights lobby, which was active on the same-sex marriage issue in Maryland this year. The HRC reported spending more than $494,000 on lobbying.

Others in the Top 10 included some perennial big spenders on lobbying in Annapolis. Among them: the Maryland Association of Realtors, $693,310; the Maryland State Education Association, $564,477; the Maryland Hospital Association, $553,568; Verizon Maryland, $503,322; and the Baltimore Jewish Council, $432,013.