More than 2,400 former senior Defense Department civilian and military officials work for 52 government contractors surveyed, and many of them work on projects they once oversaw as federal employees, a new Government Accountability Office report shows.

Nearly 65 percent of these former senior officials worked for seven of the largest government contractors: Science Applications International Corp., Northrop Grumman, Booz Allen Hamilton, L3 Communications, Lockheed Martin, General Dynamics and Raytheon.

Overall, the 52 government contractors employed 86,000 military and civilian personnel who left Defense since 2001, GAO said in a May 21 report.

Most of these employees are not bound by restrictions against performing work for their former agencies, offices or commands for up to one year after leaving. The 2,400 senior officials, however, are subject to a one-year cooling-off period before they can work on projects that relate to their previous government jobs.

Companies have protections in place to ensure those senior executives follow the rule, GAO found, but they still found it difficult to respond to GAO’s request for accurate information identifying their former Defense officials. This raised questions as to whether there is enough transparency into post-government employment to ensure former employees comply with the cooling-off period, GAO said.

For example, at least 422 former employees worked on Defense contracts let by their former agencies, offices or commands. Another nine employees performed services under contracts for which they had program oversight responsibilities or decision-making authorities while at Defense, GAO said. But it is not clear whether any of these employees were in violation of the cooling-off rules, according to the report.

“The information we obtained from contractors was not designed to identify post-government employment improprieties,” GAO said.

Even if they weren’t in violation of the restrictions, the former officials could exert influence over their former employers. Approximately 400 of the 2,400 senior executives were senior executives or general officers who served the government in positions “that could influence DoD’s mission-related decision making,” according to GAO. The remaining 2,000 senior officials were former government acquisition officials whose responsibilities and relationships with contractors gave them influence at Defense, the report said.

To avoid conflicts of interest, GAO recommended that the Defense Department consider requiring its contractors to disclose names of employees who used to work at DoD and who worked on solicitations that resulted in contract awards.

GAO also recommended that contractors certify their employees’ compliance with post-government employment rules.