The Federal Air Marshal Service is a "useless" agency staffed with under-worked officers who make few arrests, a Tennessee congressman is charging.

U.S. Rep. John J. Duncan Jr., R-Tenn., has taken to the House floor in recent days to ridicule the service as a "needless, useless agency" and argue that air marshals have "a cushy, easy job" that requires little more than sitting on a plane.

He also contends that the number of air marshals charged with committing crimes exceeds the number of arrests the agents themselves have made.

"I think they are doing almost no good at all," he said.

The air marshal service, which falls under the Transportation Security Administration, is a law enforcement agency that is probably best known for putting armed, undercover agents on selected flights to help thwart possible terrorist attacks or other hostile acts.

President George W. Bush ordered the program to be greatly expanded after the terrorist attacks in New York and Washington on Sept. 11, 2001. Before 9/11, the agency had roughly 33 air marshals. Today, there are about 4,000, although the exact number is classified.

Megan Norris, an air marshal and spokeswoman for the agency, defended the program, which has a 2009 budget of about $820 million.