More than 200 former senior government officials and members of Congress worked for the country's largest defense contractors during the past seven years, according to a report by the Project on Government Oversight (POGO), a District-based watchdog group.

At least one-third of the 224 former government officials had influence over procurement issues before taking a job in industry, the report said. The totals are based on publicly available information and may understate the number of former government officials who worked for contractors during that period, POGO officials said. They added that not all of the former officials identified in the report went directly from public service to the defense industry job.

The "revolving door," in which former government officials accept jobs with defense contractors, has been under increased scrutiny since Darleen A. Druyun, a former Air Force procurement official, was fired by Boeing Co. for illegally accepting a job with the company while still negotiating a multibillion-dollar proposal to lease and buy Boeing planes. Druyun has pleaded guilty to conspiracy and faces possible jail time. Following Druyun's case, Defense Secretary Donald H. Rumsfeld called for a review of the Pentagon's post-government employment rules.

"The revolving door has become such an accepted part of federal contracting in recent years that it is frequently difficult to determine where the government stops and the private sector begins," the report said. It recommends simplification of the rules on post-government employment and more oversight of the process.

Lockheed Martin Corp., the world's largest defense contractor, has had the most former government officials on its payroll in the past seven years, POGO said. Since 1997, 57 senior government officials have worked for the company, including six who served on Lockheed's board and 35 who were lobbyists, the report said.

Chicago-based Boeing employed 33 senior government officials in the period studied, and Northrop Grumman Corp. and Raytheon Co. employed 20 and 23, respectively. Falls Church-based General Dynamics Corp. employed 19, the report said.

Lockheed, which has its headquarters in Bethesda, said that it complies with government regulations when recruiting former government officials and that the company's own rules eliminate even the appearance of impropriety.

To attract the most qualified technical experts it is often necessary to find recruits with government experience, industry officials said. "Who do you want designing equipment that is going to be used in combat? Individuals who have been on the battlefield. Who do you want designing a new cockpit? You want someone who has flown in a cockpit, not someone from the pharmaceutical industry," said Lockheed spokesman Tom Jurkowsky, a former Navy officer.

Raytheon officials said the report incorrectly identifies five former government officials as current and former members of its board. POGO officials responded that the five individuals worked for Vertex Aerospace, which Raytheon owned, in whole or part, until recently.

Boeing said the report named one senior executive who has never worked in government and another who had a 26-year gap between his government duties and assuming a position with Boeing. The report implies that Boeing lobbies only to obtain defense contracts, but the firm is also interested in aviation security and free-trade policies, said Boeing spokesman Doug Kennett.

POGO's recommendations would make the post-government employment rules unnecessarily complex and could discourage industry experts from taking a government job, industry officials said.

"There is a public good to having a flow of information between government and industry," said Jonathan L. Etherton, vice president for legislative affairs for the Aerospace Industries Association, an industry group. "If you make the rules too draconian, you lose that benefit."

Darleen A. Druyun, facing the camera, was hired by Boeing while still negotiating a deal as an Air Force official.