West Virginia radio station WWVA 1170 first reported in August that Pepper Pike, which owns the Ohio mine where Romney held the rally referenced in the Obama ad, told employees attendance was mandatory and unpaid.
Romney has aggressively pushed his support for the coal industry in Ohio, Pennsylvania and Virginia in an attempt to draw a contrast with Obama.
Romney and congressional Republicans have said Obama administration regulations target the coal industry. The GOP and coal industry officials have pinned part of the industry's recent struggles on new environmental and emissions rules.
“President Obama’s policies have devastated the coal industry in Ohio and across the country," Amanda Henneberg, a Romney campaign spokeswoman, said Tuesday in a statement. "The President’s burdensome regulations have hindered coal production and resulted in job losses. It is clear that coal country can’t afford four more years like the last four years."
Democrats and the administration have said low natural gas prices are a more significant factor in the recent coal industry slowdown.