Adam Mosseri, the head of Instagram, received a cool reception on Wednesday during his first congressional testimony, as lawmakers tore into the company for being too slow to address children's safety.

"We all know that if Facebook saw significant threat to its growth or ad revenue, it wouldn't wait two months to take action," said Sen. Richard Blumenthal, D-Conn. "Why does it take months for Facebook to act when our kids face danger, when time is not on our side?"

In his opening testimony, Mosseri called for a new industry body that would create standards for age verification, age-appropriate experience and online parental controls. He said the body should receive input from civil society and parents, and that some of tech companies' legal protections should be contingent on compliance with standards the board sets.

He presented child safety as an "industry-wide issue," impacting competitors like YouTube and TikTok as well.

"We've been calling for regulation for nearly three years now, and from where I sit, there's no area more important than youth safety," he said.

Yet this vision did little to appease lawmakers, as senators from both parties expressed a strong desire to regulate the company, with several casting doubt on the idea of an industry-led body. Sen. Ed. Markey, D-Mass., said such an entity would be a continuation of the "status quo" and insufficient to address the revelations about the company's products. Blumenthal pressed Mosseri on whether the company would support the creation of an independent overseer that would be independently funded and have members independently appointed.

"Self-policing depends on trust," he said. "The trust is gone."

After years of increased scrutiny of the tech industry, lawmakers appeared far more sophisticated than in previous testimony, asking pointed questions about Facebook's proposal for regulation and internal documents. Yet lawmakers from both parties were plainly unsatisfied with what they said is insufficient action from the company.

Sen. Marsha Blackburn, R-Tenn., the top Republican on the subcommittee, said she was growing "frustrated" with the company. And that her constituents are too.

"The conversation continues to repeat itself ad nauseam," she said. "They continue to hear from you that change is coming. . . . But guess what, nothing changes. Nothing."

Mosseri is the highest-ranking executive at Meta, the parent company of Facebook and Instagram, to testify before Congress after revelations by Facebook whistleblower Frances Haugen, who exposed a trove of documents that she says show the company systematically prioritized profit over the safety of its users. Lawmakers are particularly enraged about internal company research suggesting that Instagram is harmful to a significant portion of young users, especially teen girls. Wednesday's hearing is part of a broader Senate probe into youth safety online, which has also included a hearing with executives from TikTok and YouTube.

Blumenthal told reporters Wednesday that his panel may still seek additional testimony from Meta and its subsidiaries as part of its investigation into children's online safety.

"We're not done yet here. My guess is we're going to hear potentially from former Facebook employees," Blumenthal said, though he declined to name any potential witnesses.

Tech executive hearings have become a regular fixture on Capitol Hill over the past three years, but Mosseri was one of the most high-profile leaders to appear in person since the start of the pandemic. He began his Senate charm offensive before the panel gaveled in, meeting on Tuesday with lawmakers including Sen. John Thune of South Dakota, the No. 2 Senate Republican, and Sen. Ben Ray Luján, D-N.M., according to two aides, who were not authorized to comment publicly. The meetings touched on proposals under consideration aimed at addressing concerns about how digital platforms algorithmically amplify content, the aides said.

Mosseri touted the company's increased investment in child safety, which some lawmakers dismissed as a public relations stunt in the face of potential political blowback. Mosseri said Instagram was investing heavily to be able to identify the ages of users, but he said he believed it would be more effective at the device level, where parents could set the age limits on phones or tablets to ensure they applied across all apps. When pressed by Thune about the company's algorithms, he said he believes in giving users more control and plans to launch an option to rank the feed chronologically next year.

With the senators' questions focusing heavily on Instagram's risks for young users, Mosseri argued they were overlooking its benefits. "The definition of beauty here in the U.S. used to be very limited . . . and very unrealistic," he said. "Social media platforms like Instagram have helped important movements like body positivity to flourish. . . . It has helped diversify the definitions of beauty."

While leaked documents showed Facebook researchers knew that Instagram appeared to make body image issues worse for vulnerable teen girls, the company has repeatedly emphasized that the same research shows Instagram also made many of its young users feel better when they were struggling with issues such as depression, anxiety and loneliness.

He also repeatedly mentioned some of the company's new features addressing mental well-being, including reminders to "take a break" when people are deemed to have been scrolling on the app for too long. Yet Blackburn criticized a series of new tools the company introduced to keep children and teens safer online as "half measures." She said it's time to pass legislation to keep children safe online, as well as a federal privacy bill.

"This is a case of too little, too late," Blackburn said. "Because now there is bipartisan momentum - both here and in the House - to tackle these problems we are seeing with Big Tech."

On Wednesday, Blumenthal said in his opening remarks that his office had set up a fake Instagram account posing as a 13-year-old girl, repeating the test presented to Facebook head of safety Antigone Davis in September, with similar results. This time "within an hour" of opening the account it began encountering content that glorified disordered eating and extreme dieting. Blackburn said Wednesday that her office had also created a false account posing as a 15-year-old girl and that Instagram had automatically set the profile to "public" rather than "private."

Mosseri said the test by Blackburn's office had exposed what appeared to be an "oversight" in Instagram's systems, in which users under the age of 16 who signed up for the service via the Web - as opposed to an Instagram app - had their profiles default to public instead of private. Mosseri said the company had just learned of the issue and was working to correct it.