Senators Elizabeth Warren and Bob Casey want more federal oversight of the country’s guardianship system following Britney Spears’ emotional testimony about her conservatorship, they wrote in a letter on Thursday.

The lawmakers are calling on the Department of Health and Human Services (HHS) and the Department of Justice (DOJ) to provide information about data the agencies collect on the prevalence of guardianship in the U.S, any efforts the agencies have made to protect people under guardianship and ways Congress can improve federal collection of guardianship data.

“Ms. Spears’ case has shined a light on longstanding concerns from advocates who have underscored the potential for financial and civil rights abuses of individuals placed under guardianship or conservatorship,” Warren and Casey wrote in a letter shared exclusively with TIME. “Despite these concerns, comprehensive data regarding guardianship (referred to as conservatorship in some states) in the United States are substantially lacking—hindering policymakers and advocates’ efforts to understand gaps and abuses in the system and find ways to address them.”

Spears has lived under a conservatorship since 2008 when a court granted her father legal authority over her personal life and finances amid concerns about her mental health. Last week, some details about her conservatorship were made public for the first time when the singer asked a Los Angeles judge to end the arrangement. She claimed that over the past 13 years, she had been drugged, forced to perform against her will and denied the right to remove her birth control device.