Democratic Senators Elizabeth Warren and Bob Casey are calling on federal agencies to increase oversight of the country’s conservatorship systems, following testimony from the pop star Britney Spears that she had been abused under her conservatorship.

The senators, in a letter to Xavier Becerra, the health secretary, and Merrick B. Garland, the attorney general, asked for more data within the next two weeks on conservatorships in the United States, and how their agencies interact with the state programs. The move could signal the beginning of a legislative effort to overhaul the system.

“Ms. Spears’s 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,” Ms. Warren of Massachusetts and Mr. Casey of Pennsylvania wrote.

The senators also highlighted previous efforts to study and change the conservatorship system that they said had fallen short.

Ms. Warren, in a separate statement, described a system with “longstanding gaps that can strip people of basic rights.”

Both the Departments of Justice and Health and Human Services“have previously stepped in to provide federal support for guardianship reforms and establish national reporting as it relates to older Americans,” she said. “But the lack of federal data on the prevalence of conservatorships and guardianships of all kinds has made it difficult to enact policy changes.”

The National Center for State Courts estimates that there are 1.3 million active conservatorships in the United States overseeing at least $50 billion in assets, but the group notes that the estimate is based on a “handful” of states that provide reasonably reliable data on conservatorships. Each state manages its own system of conservatorship, and data collection varies widely from state to state.

In particular, the senators highlighted a lack of data on the potential for discrimination in the conservatorship system on the basis of “race and ethnicity, age, sex, gender identity, sexual orientation, and type of disability of those subject to a guardianship.”

That assessment is supported by independent government agencies who have studied conservatorships. A report by the Government Accountability Office in 2016 noted that “the extent of elder abuse by guardians nationally is unknown.” The National Council on Disability said in 2018 that it “cannot say for sure whether guardianship is a growing trend or if its popularity is waning,” adding that the lack of data makes it difficult to recommend policy changes.

Ms. Spears told a Los Angeles judge last week that she had been drugged, compelled to work against her will and prevented from removing a birth control device during the 13-year conservatorship.

On Thursday, a wealth management firm that was set to become a co-conservator of Ms. Spears’s estate requested to withdraw from the arrangement. In the request to the court, the firm said it had been told that Ms. Spears’s conservatorship was voluntary.

James P. Spears, Ms. Spears’s father who oversees the singer’s finances, called for an investigation into her claims. His lawyers have requested an evidentiary hearing and called into question the actions of both Ms. Spears’s current personal conservator, who replaced Mr. Spears in the position in 2019, and her court-appointed lawyer.