WASHINGTON — A senator is asking Facebook CEO Mark Zuckerberg for testimony before a panel. The panel has already heard extensive criticisms from a former employee.

Senator Richard Blumenthal (D-Conn.), who heads the Senate Commerce subcommittee for consumer protection, sent a clear-worded letter Wednesday asking the Facebook founder to testify about Instagram’s effects upon children.

Blumenthal wrote to Zuckerberg, stating that “Parents across America are deeply troubled by ongoing reports Facebook knows that Instagram could cause destructive and lasting harms for many teens and children, particularly their mental health and well-being.” “Those parents and twenty million teens who use your app have the right to know the truth about Instagram’s safety.”

Blumenthal said to Zuckerberg that in the wake of Frances Haugen’s testimony earlier this month, Facebook representatives including you had doubled down on evasive responses. They kept hidden many reports about teen health and offered vague and non-committal plans for action at a unspecified date.