Black employees of the U.S. Marshals Service filed a racial discrimination lawsuit Wednesday, saying they have been denied promotions by managers who belittled them as lazy.

The lawsuit in U.S. District Court accuses the federal law enforcement agency of a "good old boys network" that allegedly groomed whites for leadership positions while passing up and reprimanding blacks for "trivial mistakes."

"This is the way the agency treats African-American deputies all over the country," said David Grogan, a deputy U.S. marshal who is filing the lawsuit. "If you're an African American doing a good job, they're going to find some loophole or exception to keep you from getting ahead."

In one incident, Grogan said he was taunted and insulted by a manager for using the gym. U.S. Marshals policy allows deputies up to three hours a week of gym time, but the manager said he "set a bad example" because he spent too much time exercising and did not take his job seriously.

"In this way, Chief M.G. and several of his white friends attempted to use Mr. Grogan's physical fitness to reinforce their racial stereotypes of Mr. Grogan as lazy," the 42-page complaint states.

The Marshals Service, a division of the Justice Department, has 4,700 employees and is responsible for apprehending fugitives and protecting federal judges.

Jeff Carter, a spokesman for the Marshals Service, said the agency could not comment on specific allegations while the lawsuit is pending.

"I can tell you that U.S. Marshals is aware of the allegations contained in the lawsuit, and these allegations do not reflect the culture of this agency or the high standards to which we hold our employees," he said.

The lawsuit alleges violation of federal civil rights laws and is seeking to represent 200 current or former black U.S. Marshals employees. It is asking for damages of at least $300 million in lost back pay and harm that employees suffered in a "hostile work environment."