US lawmakers pounded Facebook on Tuesday, accusing Chief Executive Officer (CEO) Mark Zuckerberg of pushing for higher profits while being cavalier about user safety, and demanded that regulators investigate whistleblower accusations that the social media company harms children and stokes divisions.

During a Senate Commerce subcommittee hearing, whistleblower Frances Haugen called for transparency about how Facebook entices users to extend their stay on the site, giving them ample opportunity to advertise to them.

"As long as Facebook is operating in the shadows, hiding its research from public scrutiny, it is unaccountable," said Haugen.

She said she opposed the breakup of Facebook as counterproductive.

"The company’s leadership knows how to make Facebook and Instagram safer, but won’t make the necessary changes because they have put their astronomical profits before people. Congressional action is needed," Haugen said.

In an era when bipartisanship is rare in Washington, lawmakers from both parties excoriated the nearly $1 trillion company, illustrating the rising anger in Congress with Facebook amid numerous demands for legislative reforms.

Senator Dan Sullivan, a Republican, said he was concerned about how Facebook and subsidiaries like Instagram affected the mental health of children. "I think we're going to look back 20 years from now and all of us are going to be like 'what the hell were we thinking?'"

Haugen revealed she was the one who provided documents used in a Wall Street Journal investigation and a Senate hearing on Instagram's harm to teenage girls.

Panel chair Senator Richard Blumenthal, a Democrat, said Facebook knew that its products were addictive, like cigarettes.

"Tech now faces that big tobacco jaw-dropping moment of truth," he said.

He called for Zuckerberg to testify before the committee, and for the Securities and Exchange Commission and Federal Trade Commission to investigate the company.

"Our children are the ones who are victims. Teens today looking in the mirror feel doubt and insecurity. Mark Zuckerberg ought to be looking at himself in the mirror," Blumenthal said.

Coming a day after Facebook suffered an hours-long outage, Haugen used the breakdown in her testimony to emphasise her point: "For more than five hours Facebook wasn't used to deepen divides, destabilise democracies and make young girls and women feel bad about their bodies."

As lawmakers criticised Facebook and Zuckerberg, the company's spokespeople fought back on Twitter, arguing Haugen did not work directly on some of the issues she was being questioned on.

Haugen, a former product manager on Facebook's civic misinformation team, left the company with tens of thousands of confidential documents.

Senator Marsha Blackburn, a Republican, accused Facebook of turning a blind eye to children below age 13 on its sites. "It is clear that Facebook prioritises profit over the wellbeing of children and all users," she said.

Facebook spokesperson Kevin McAlister said in an email ahead of the hearing that the company sees protecting its community as more important than maximising profits and said it was not accurate that leaked internal research demonstrated that Instagram was "toxic" for teenage girls.

Last week, Antigone Davis, Facebook's global head of safety, defended the company in front of Congress and said that it was seeking to release additional internal studies in an effort to be more transparent about its findings.

Senator Maria Cantwell, chair of the Commerce Committee, said she would write a letter to Facebook to insist that it not delete documents related to Myanmar's persecuted Muslim minority Rohingya. An aide said she would ask for broader retention of documents.

Read: Facebook ordered to release anti-Rohingya posts for genocide case

Haugen said she would encourage "oversight and public scrutiny" into how the content algorithms work and the consequences of them. She suggested creating a dedicated body within the federal government to oversee social media companies.

Blumenthal said that he might want to hold an additional hearing to discuss national security issues related to Facebook.

Haugen said Facebook had also done too little to prevent its site from being used by people planning violence.

Facebook was used by people planning mass killings in Myanmar and the January 6 assault on the US Capitol by supporters of then-president Donald Trump who were determined to toss out the 2020 election results.

Senator Edward Markey, speaking to the absent Zuckerberg, said during the hearing: "Your time of invading our privacy, and preying on children is over. Congress will be taking action."

Throughout the hearing, lawmakers referred to Zuckerberg as going sailing instead of facing his responsibilities. The CEO this weekend posted a video taken with the company's new smart glasses of his wife in a boat.

Despite the criticism, Facebook's share price was up 2.3 per cent at $333.90 around midday on Tuesday.