More than 5,500 people have access to classified files at Department of Energy headquarters here although they no longer work for the department, according to the DOE inspector general.

The report, released this week, said that at least one-third of the department's 16,000 security clearances are held by people no longer affiliated with the DOE, its contractors or other federal agencies.

The clearances, some granted by the DOE's predecessor agencies as much as 30 years ago, allow their holders "access to DOE facilities and, possibly, to classified data," Inspector General John C. Layton told Energy Secretary John S. Herrington.

The DOE requires security clearances for access to several levels of classified information, ranging from less sensitive "formerly restricted data" to highly guarded national security information. Department officials said the inquiry was prompted by the administration's effort to get a better handle on internal security, not by any evidence that unauthorized people were poking around the department's classified files.

But the results suggest that the DOE's policy of withdrawing unnecessary security clearances is being enforced haphazardly at best.

According to the report, 2,300 of the 3,800 security clearances granted to contract employes are invalid because the contract has expired or the employe no longer works for the contractor.

"Almost half of the individuals who sponsored the clearances no longer worked for DOE, and several of the sponsoring organizations themselves no longer existed," the report said.

More than 2,200 -- or 40 percent -- of the 5,700 security clearances granted to DOE employes are invalid because the employes quit or were transferred to jobs not requiring security clearances.

Investigators also found widespread inaccuracies in clearances granted to DOE employes. "Over 1,500 records did not have a Social Security number," the report said. "Other records . . . showed the clearance holder belonging to the wrong organization."

The report did, however, give one security category a clean bill of health. Of the 536 security clearances granted to employes of Congress, none was found invalid.