Washington ? Private contractors account for more than one-quarter of the core work force at U.S. intelligence agencies, according to newly released government figures that underscore how much of the nation’s spying work has been outsourced since the Sept. 11 attacks.

The CIA and other spy agencies employ about 36,000 contractors in espionage-related jobs, in addition to approximately 100,000 full-time government workers, according to Ronald Sanders, the head of personnel for the U.S. intelligence community.

Contractors carry out missions ranging from collecting intelligence in Iraq and Afghanistan to operating classified computer networks for the U.S. intelligence community.

Sanders said the number of contractors remained steady over the past year, after surging heavily in the years following the Sept. 11 attacks.

The growing reliance on contractors has been a source of controversy for U.S. spy agencies, in part because of concerns that temporary employees might not be as trustworthy as career workers.