Federal agencies spend millions of dollars each year training civil service senior executives, but don't accurately report the costs or evaluate whether it does any good, according to the Government Accountability Office.

"The cost of these training sessions has raised questions about the value they provide to the federal workforce," Yvonne D. Jones, GAO's director of strategic issues, wrote in the report.

Twenty-six agencies reported spending almost $57 million on training for 30,000 members of the government's Senior Executive Service between 2008 and 2012, according to GAO.

Total annual SES training costs ranged from $9 million to $15 million.

But several problems kept GAO from determining the full cost of SES training. Some agencies don't report costs of materials, travel or lodging, while others use incompatible digital systems to track the spending costs, or even paper records that require manually calculating costs.

Others have components within the agency that use specially allocated funding sources and don't report certain training to the rest of the agency.

"In light of all these factors, agencies are likely underreporting the amount they spent on executive training," the report said.

After spending so much, agencies should be evaluating the impact of the training on the agency, GAO said.

But less than half of the agencies said they do so. Those who didn't said the cost, difficulty and time required to do the evaluations kept them from assessing whether training benefits the agencies.

"Without conducting higher levels of evaluation, agencies are missing information that could help them make more effective training investment decisions," the report said.

GAO recommended that the Office of Personnel Management, which manages the SES, work with agencies to improve their cost reporting and their evaluation of the training.