With Congress asking for more investigations on topics ranging from defense to health care to technology, the Government Accountability Office is seeking 500 new staff positions — an 18 percent increase — over the next six years, Comptroller General David Walker said Friday.

Walker did not officially ask for the employee boost in the agency’s fiscal 2008 budget request, which he presented to the Senate Appropriations subcommittee on the legislative branch.

But he told the panel that past funding shortfalls have left the agency stretched and backlogged in several areas, including health care, homeland security, energy and natural resources, and eventually will need more staffers to handle the workload.

“We need to have a reasonable number of resources to get the job done,” Walker told subcommittee Chairwoman Mary Landrieu (D-La.), the only panel member to attend Friday’s hearing.

Walker joined officials from the Government Printing Office, Congressional Budget Office and Office of Compliance at the hearing.

The GAO is by far the largest agency among the four. GAO officials are seeking about $523 million, an 8.5 percent increase over funding levels in fiscal 2007.

Most of that money would go to restore GAO’s funding to more appropriate levels, Walker said, particularly after the agency received only a slight increase this year under the fiscal 2007 continuing resolution.

Despite funding challenges, Walker told the committee that the GAO still managed to help the federal government gain $51 billion in financial benefits in 2006, which amounts to $105 for every $1 the agency was allocated.

Walker said after the hearing that the request for 500 new employees is a preliminary target that could get revised over time.

“I’m trying to say, ‘Looking ahead, here’s what I see,” Walker said.

Walker added when he first took office in 1996, he told Congress that he would not ask for more employees until he felt confident the agency itself ran productively and efficiently.

But the time is right to bring more employees on, Walker said. One reason: the GAO likely will be called on to study the Department of Defense’s financial and other internal systems, something that will require a work force increase, he said.

If Congress decides to add more staff, it probably will happen in installments, Walker said.

“We can only absorb so many people a year,” he added.

Landrieu praised Walker for doing “an excellent job” running the GAO, but she specifically asked about the agency’s 2004 transition to a pay structure based on a more market-based, performance-driven system.

While Walker has held up the new pay method as a model for other agencies, it has spawned a unionization effort at the agency and led to accusations that some GAO analysts had been discriminated against.

Walker defended the pay structure on Friday, telling Landrieu that the agency is considered “one of the best places to work in the government” and that most employees benefitted from the change.

Only about 100 employees were found to be overpaid, and they are the ones who likely are behind the effort, Walker said.

“There were many more positives than negatives,” Walker said.

He added after the hearing that individuals outside the GAO could be involved in calls for unionization, particularly because agency policies are often used as a model for other federal agencies.

“This is not just an issue of GAO,” Walker said. “I think some people have concern about the broader implications, because we are the leader.”

Landrieu told Walker that she has found the pay system to be professionally run.

“I certainly find no fault,” Landrieu said, adding that she uses some of the same pay-for-performance techniques with her own staff.

The three other agencies at the hearing also asked for budget increases.

The Government Printing Office requested the biggest budget hike out of any agency — a 48.6 increase to $182 million.

While Landrieu questioned the need for such a large boost, acting Public Printer William Turri said much of the additional money is needed to fund things the agency has no control over.

That includes the printing of the U.S. Code, which takes place every six years, and printing additional documents for the Congressional Record, largely because the amount of work Congress has and is expected to do this session has increased.

The Congressional Budget Office asked for a 7.9 percent increase in funds to $38 million.

Most of this would go to funding for additional staff, including employees who would study ways Congress could address growth in health care spending, newly appointed Director Peter Orszag told the panel.

The Office of Compliance asked the panel to help with an issue not directly related to finances, however.

At the request of its Board of Directors, the OOC is seeking authority to strike a statute in the U.S. Code in an effort to allow more internal promotion within the agency.

The statute currently limits the OOC’s board from promoting into an appointed positions anyone who has worked on Capitol Hill. In the long run, deleting the provision will allow for more upward movement in the agency. In the short run, it will allow the board to name acting Executive Director Tamara Chrisler — who has served under that title for the past year — the permanent head of the agency.

John McArdle contributed to this report.