Federal health insurance officials can't tell Congress how much the government has spent since 2010 selling Obamacare to a key segment of the market, according to the Government Accountability Office.

The accounting system used by the Center for Medicare and Medicaid, which manages Obamacare, doesn't track "expenditure totals for CCIIO-related polling, focus groups, or advertising and other public relations activities," GAO said in a report made public Monday.

The CCIIO is the Center for Consumer Information and Insurance Oversight, which is part of the Center for Medicare and Medicaid. It's main focus is overseeing implementation of the Obamacare provisions that apply to the private health insurance market and the health insurance exchanges created by the program.

Federal officials were also unable to say if they have enough employees to carry out CCIIO's duties under Obamacare because, GAO said, "the staff reassignment information provided to GAO was not complete, was not supported by documentary evidence, and could not be verified."

The only verifiable data GAO said CMS could provide was "CMS's estimates for total obligations for fiscal year 2014, which was $3.7 billion; the number of staff as of September 30, 2013, which was 347; and total salary expenditures from March 2010 through fiscal year 2013, which were $79.8 million."

Otherwise, GAO said, the inability of CMS to provide credible data on what CCIIO is doing in a timely fashion means "Congress and other decision makers may not have access to timely and reliable CCIIO-related information that they may need to make resource allocation decisions and assessments of program performance."

House Ways and Means Committee Chairman Dave Camp, R-Mich., said the GAO report demonstrates that "the Obama administration has tried to hide the ball from Congress on just how much it is spending on the health care law.

"After promising transparency and then ignoring repeated requests from Congress, we now find out that the administration is not even keeping track of how many taxpayer dollars are going out the door.

"Worse yet, the administration won’t even account for how much it spent on public relations campaigns promoting their unpopular law. “

Camp, who with Rep. Charles Boustany, R-Lou., requested the GAO study, is expected to release a more detailed statement on the report Tuesday.

Boustany is chairman of the ways and means panel's oversight subcommittee.

Go here to read the full GAO report.

Mark Tapscott is executive editor of the Washington Examiner.