WASHINGTON — A government watchdog has expanded an ethics probe of the National Labor Relations Board after finding that more inside information was leaked to a former adviser to Republican presidential hopeful Mitt Romney, a Democratic lawmaker said Thursday.

Maryland Rep. Elijah Cummings said the board’s inspector general discovered additional improper disclosures by Republican board member Terence Flynn to former NLRB board member Peter Schaumber, who was a senior labor adviser to Romney’s campaign.

Cummings, the top Democrat on the House Oversight and Government Reform Committee, said the inspector general referred his findings to the U.S. Office of Special Counsel for potential violations of the Hatch Act, which prohibits federal employees from engaging in partisan political activity.

Romney’s campaign disclosed for the first time Thursday that Schaumber stepped down in December from his advisory post, around the time the investigation began. As recently as March, union groups had called on Romney to dismiss Schaumber, and the campaign did not respond when The Associated Press inquired about his status last month.