Statistics collected by the Department of Labor on the hiring of military veterans by government contractors are frequently inaccurate, according to the chairman of a Senate subcommittee, leaving the government without reliable data on progress in putting veterans to work for firms doing federal business.

Under federal law, companies with government contracts are required to report information about their hiring and employment of veterans. Larger federal contractors are required to develop actions plans for hiring veterans

“The question is, how well are contractors doing at this?” Sen. Claire McCaskill (D-Mo.), chairman of the Senate Subcommittee on Contracting Oversight, said in a prepared statement at a hearing on the issue Tuesday. “The answer is that we have no idea.”

The Obama administration has pledged to lower the unemployment rate among veterans. The rate for veterans who have served on active duty since September 2001 stood at 12.7 percent in May, compared to 8.2 percent for the nation overall.

McCaskill, (D-Mo.), said that even though the reporting requirement has been in place since 2002, the Labor Department was able to provide data only for 2009 and 2010.

Those data, she said, are “spotty and frequently inaccurate. We saw numbers that are obviously wrong.”

For example, the Labor Department data indicate that the Compass Group, a food service management contractor, hired 78,383 veterans in 2010, more than any other firm. But that number was nearly four times higher than the the company’s total new hires for 2010, according to a fact sheet issued by McCaskill’s office.

A Compass representative told subcommittee staff that the company had experienced difficulty submitting the information to the Labor Department, providing it electronically multiple times and finally giving it manually, according to the fact sheet.

The Department of Labor believes McCaskill has “raised important issues,” according to a spokesman.

“The department understands that good data is the cornerstone of good policy, and good policy leads to effective enforcement,” the department said in a statement.

“That is why we are working to ensure that we collect timely and accurate data on veterans employment and to strengthen our regulations so that all veterans have access to good jobs.”