Federal agencies spend millions of tax dollars opposing Americans’ successful lawsuits seeking public records under the Freedom of Information Act (FOIA), but can’t say exactly how much, according to a new Government Accountability Office (GAO) report.

Department of Justice (DOJ) officials responsible for tracking agencies’ FOIA compliance don’t know how much agencies spent fighting 112 cases from 2009 to 2014 in which the plaintiff “substantially” prevailed, according to GAO. Of the 57 lawsuits agencies could track, agencies spent $1.8 million.

But that’s just a drop in the bucket compared to the $144 million agencies estimated they spent fighting 3,350 FOIA lawsuits from 2009 to 2014, according to GAO.

Current DOJ policy doesn’t require department officials to track spending by agencies on specific lawsuits, or whether the plaintiff or agency prevailed, leaving gaps in federal records about FOIA lawsuits, according to GAO.

“Although requiring Justice and agencies to report actual cost information could lead to better transparency regarding federal operations, costs would be associated with such reporting,” the GAO report said. “Considering these costs, as well as potential benefits, could help Congress in determining whether such a requirement would be cost-effective for enhancing oversight of FOIA litigation-related operations.”

FOIA is the main tool for journalists and members of the public to request government documents, and agencies have 20 business days to respond. But agencies often fail to meet that deadline, at which point the requester can file a lawsuit against the government. (RELATED: Agency Admits It Destroyed Records After Six-Year FOIA Stonewall)

The Department of State is the slowest agency in responding to FOIA requests, taking 111 days on average, according to a DOJ report released earlier this year.

The number of FOIA lawsuits against federal agencies continues to climb. Plaintiffs filed 290 FOIA lawsuits against agencies in 2006, but 456 in 2015, according to GAO.

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