Facebook’s products “harm children, stoke division and weaken our democracy”, a whistleblower has claimed.

Frances Haugen – who used to work as a product manager at the tech giant – has given damning evidence to US politicians in the Senate, days after leaking internal documents to the Wall Street Journal.

She warned: “Left alone, Facebook will continue to make choices that go against the common good. Our common good.

“When we realised Big Tobacco was hiding the harms, that caused the government to take action. When we figured out cars were safer with seatbelts, the government took action.

“And when our government learned that opioids were taking lives, the government took action.”

Facebook whistleblower reveals embarrassing evidence to US politicians – live updates

Ms Haugen implored politicians in the hearing to take similar action – and alleged that the company’s leadership knows how to make its platforms safer, but won’t make the necessary changes “because they have put their astronomical profits before people”.

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She later warned that there was nobody at the company who could hold Mark Zuckerberg accountable other than himself.

“Mark holds a very unique role in the tech industry in that he holds over 55% of all the voting shares for Facebook. There are no similarly powerful companies that are as unilaterally controlled,” she said.

Senator Richard Blumenthal, a Democrat, said Facebook knew that its products were addictive like cigarettes – adding: “Tech now faces that Big Tobacco jaw-dropping moment of truth.”

He also assured Ms Haugen that politicians will do “anything and everything to protect and stop any retaliation against you, and any legal action that the company may bring to bear”.

The whistleblower had revealed her identity in an interview with the 60 Minutes programme on CBS, where she claimed Facebook prematurely turned off safeguards designed to combat misinformation that contributed to the US Capitol attack.

Among Ms Haugen’s key warnings was how Facebook optimised its algorithms to increase engagement through discord and arguments, something that benefited the company’s revenues.

Facebook has responded to a series of stories published by the Wall Street Journal based on her leaked documents, including one that suggested the company knew Instagram had a negative image on the body image of teenage girls.

Facebook denied that it “conducts research and then systematically and wilfully ignores it if the findings are inconvenient for the company” as it paraphrased the reports.

Analysis: This is devastating for Facebook

By Mark Stone, US correspondent

Within minutes of it starting, it was clear immediately that this would be a devastating hearing. With each sentence spoken by former Facebook employee Frances Haugen came more damning allegations.

She is not calling for the shutdown of Facebook. Ms Haugen says she believes there is a place for a responsible social media company. She highlighted the moments we all enjoy – the sharing of family photos. Staying in touch with distant friends. But beyond that – sentence by sentence – Ms Haugen is delivering a truly horrific assessment of Facebook’s practices.

“Almost no one outside Facebook knows what happens inside Facebook,” Ms Haugen said. “The company’s leadership keeps vital information from the public,” she added. “Facebook has repeatedly misled us about what it’s own research reveals about the safety of children,” she alleged.

She described how bullying online through Facebook and Instagram follows children home. It’s often the last thing they read when they go to bed. When she was at school, she said, kids could find a safe place at home at the end of the school day. Now, the pressures and impact is in their palm and with them all the time.

The focus is the safety of children but she broadened her testimony to include the influence Facebook has on politics and hate speech and its extraordinarily pervasive influence on societies in countries like Myanmar and Ethiopia.

Ms Haugen was, until May this year, a product manager hired by Facebook to help protect against election interference on the platform. The chairman of the committee, Democratic senator Richard Blumenthal, said in his opening remarks: “The damage inflicted by Facebook will haunt a generation.”

This feels like a tipping point for the social media firm.