The Department of Health and Human Services needs to adopt a “more aggressive strategy” against Medicare and Medicaid overbilling, the director of the Office of Management and Budget wrote in a letter to HHS Secretary Sylvia M. Burwell only recently obtained by the Center for Public Integrity.

Written by budget director Shaun Donovan in February, the letter calls for HHS to develop a “comprehensive corrective action plan” to combat increasing improper payments. Donovan noted that billing errors in the Medicare Fee-for-Service program rose 2.62% in 2014, resulting in $9.7 billion more spent on improper payments than the previous year. Medicaid also saw a $3.1 billion increase in improper billing, he wrote.

“We must continue to explore new and innovative ways to address the problem and continue to attack this challenge with every tool at our disposal,” Donovan wrote.

In addition to a corrective action plan, Donovan recommended HHS develop plans to ensure proper payments under the Affordable Care Act, and engage the Office of Inspector General to receive feedback on the program’s performance.

Click here to read the full letter.