“So here’s my message for Mark Zuckerberg: Your time of invading our privacy, promoting toxic content and preying on children and teens is over,” said Senator Edward J. Markey, Democrat of Massachusetts.

Mr. Blumenthal said after the hearing, “Facebook is a black box, and Mark Zuckerberg is the algorithm designer in chief.”

Ms. Haugen studied electrical and computer engineering at Olin College and got a master of business administration degree from Harvard. She then worked at Silicon Valley companies including Google, Pinterest and Yelp. She left Facebook after nearly two years handling counterespionage as part of the civic misinformation team, according to her personal website.

At Facebook, Ms. Haugen said, she noticed a pattern of the company’s choosing to ignore warnings of harm done by its service. The final straw came in December when the company disbanded her group, which was charged with stopping the spread of misinformation.

“It really felt like a betrayal,” Ms. Haugen said.

In addition to sharing the documents with lawmakers and The Journal, she sent some to the offices of at least five state attorneys general and the Securities and Exchange Commission. Lawyers at Whistleblower Aid, a nonprofit law group that represents Ms. Haugen, have pressed the S.E.C. to open an investigation that Facebook withheld evidence that would affect its financial performance.

Mr. Blumenthal said after the hearing that he would ask the Federal Trade Commission and the S.E.C. to open investigations into Facebook for “a number of misleading claims” that have been made to consumers, the public and investors. He added that Mr. Zuckerberg should appear before Congress.

“If he is in any way in disagreement with anything that has been said here, he’s the one that ought to come forward, he’s the one that’s in charge,” Mr. Blumenthal said.

Reporting was contributed by Mike Isaac, Sheera Frenkel, Ryan Mac and Kevin Roose.


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