The Senate on Tuesday confirmed Lina Khan, a prominent critic of the nation’s largest tech companies, to the Federal Trade Commission, giving her a central position at the agency that investigates antitrust violations, deceptive trade practices and data privacy lapses in Silicon Valley.

Lawmakers voted 69-28 to confirm Ms. Khan, 32, who first attracted notice as a critic of Amazon. The agency is investigating the retail giant and filed an antitrust lawsuit against Facebook last year.

Ms. Khan will help regulate the kind of behavior highlighted for years by critics of Amazon, Facebook, Google and Apple. She told a Senate committee in April that she was worried about the way tech companies could use their power to dominate new markets.

Her appointment was a victory for progressive activists who want Mr. Biden will take a hard line against big companies. He also gave a White House job to Tim Wu, a law professor who has criticized the power of the tech giants.

But Mr. Biden has yet to fill two key positions tasked with regulating the industry. He has not named the F.T.C.’s permanent chair or nominated someone to lead the Department of Justice’s antitrust division.