A California representative is calling for an investigation into Accretive Health, one of the nation’s largest collectors of medical debt, for potentially violating a federal law that requires hospitals to provide emergency care regardless of citizenship, legal status or the ability to pay.

The congressman, Pete Stark, a Democrat who is the highest ranking member of the subcommittee that oversees Medicare and other health services, on Thursday asked Marilyn B. Tavenner, the acting administrator for the Medicare and Medicaid agency, to investigate the company’s practices.

He sent an identical letter to the inspector general of the Department of Health and Human Services, Daniel R. Levinson.

In an interview, Mr. Stark said that he was most alarmed about Accretive’s tactics of demanding that patients seeking emergency care pay outstanding balances before receiving treatment. Mr. Stark said he was spurred to action after reading about Accretive’s practices in an article in The New York Times on Wednesday.