Former Facebook employee and whistleblower Frances Haugen is expected to tell US Congress on Tuesday that the company faces little oversight and liken the social media giant to tobacco companies that for decades denied that smoking damaged health, according to testimony seen by Reuters.

"When we realized tobacco companies were hiding the harms it caused, the government took action. When we figured out cars were safer with seatbelts, the government took action," said Haugen's written testimony before a Senate Commerce subcommittee set for Tuesday. "I implore you to do the same here."

Haugen will tell a Senate Commerce Committee panel that when Facebook executives had to choose between profits or user safety, profits won out.

"The company's leadership knows ways to make Facebook and Instagram safer and won't make the necessary changes because they have put their immense profits before people. Congressional action is needed," she will say, according to prepared testimony seen by Reuters. "As long as Facebook is operating in the dark, it is accountable to no one. And it will continue to make choices that go against the common good."

Haugen, who worked as a product manager on Facebook's civic misinformation team, appeared on Sunday on the CBS television program "60 Minutes", revealing her identity as the whistleblower who provided the documents that underpinned a Wall Street Journal investigation and a Senate hearing on Instagram's harm to teen girls.

Facebook has been under fire after the Journal published a series of stories based on Facebook internal presentations and emails that showed the social media company contributed to increased polarisation online when it made changes to its content algorithm, failed to take steps to reduce vaccine hesitancy and was aware that Instagram harmed the mental health of teenage girls.

Facebook did not immediately respond to a request for comment.

'Profit over hate speech'

Haugen accused the social media giant of repeatedly prioritising profit over clamping down on hate speech and misinformation, and said her lawyers have filed at least eight complaints with the US Securities and Exchange Commission.

"There were conflicts of interest between what was good for the public and what was good for Facebook," she said during the interview. "And Facebook over and over again chose to optimise for its own interests like making more money."

Haugen, who previously worked at Google and Pinterest, said Facebook has lied to the public about the progress it made to clamp down on hate speech and misinformation on its platform.

She added that Facebook was used to help organise the Capitol riot on January 6, after the company turned off safety systems following the US presidential elections.

While she believed no one at Facebook was "malevolent", she said the company had misaligned incentives.

Facebook published a statement disputing the points that Haugen made after the televised interview.

"We continue to make significant improvements to tackle the spread of misinformation and harmful content," said Facebook spokesperson Lena Pietsch. "To suggest we encourage bad content and do nothing is just not true."