The campaign committee of U.S. Senate Republicans has moved to block a Republican advertising firm from receiving any future contracts from the committee, due to the firm’s working with a conservative political action group.

The National Republican Senatorial Committee (NRSC) informed Jamestown Associates, a media advertising company, that the firm would not receive any new contracts from the NRSC because of the firm’s work for the Senate Conservatives Fund, founded by former Sen. Jim DeMint, R-S.C., according to a New York Times blog item this afternoon.

The Times posting stated the NRSC had also called specific Senate campaigns to encourage them not to hire the firm. The firm is handling advertising against Senate Minority Leader Mitch McConnell, R-Ky., who is up for re-election in 2014.