Explosive testimony from a former Facebook employee turned whistleblower ...

Frances Haugen, a former product manager on Facebook's civic misinformation team, told a Congressional committee on Tuesday that Facebook knowingly amplifies divisive and harmful content, choosing profit over safety.

And...that Facebook has sought to keep its operations confidential amid mounting scrutiny, especially in regards to its effects on children.

[HAUGEN] "Congressional action is needed... Today, no regulator has a menu of solutions for how to fix Facebook, because Facebook didn't want them to know enough about what's causing the problems..."

Lawmakers in both parties pounced.

[SEN. MARKEY] "It's only real principle is profit."

[KLOBUCHAR] "Mark Zuckerberg is going sailing and saying no apologies...."

... accusing CEO and Founder Mark Zuckerberg of pushing for higher profits while being cavalier about user safety - and they demanded that regulators investigate whistleblower accusations that the social media company harms children and stokes divisions.

"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.

[FLASH]

[HAUGEN] "In the end, the buck stops with Mark. There is no one currently holding Mark accountable but himself..."

Haugen said Facebook had also done too little to prevent its site from being used by people planning violence - saying its focus on metrics trumped ethical concerns.

Facebook was used by people planning mass killings in Myanmar and the Jan. 6 assault on the U.S. Capitol by supporters of then-President Donald Trump who was determined to toss out the 2020 election results.

[HAUGEN] "Facebook can change but is clearly not going to do so on its own. My fear that without action, divisive and extremist behaviors that we see today are only the beginning. What we saw in Myanmar and are now seeing in Ethiopia is only the opening chapters of a story so terrifying no one wants to read the end of it."

Haugen says Facebook has the tools to deemphasize divisive content, but chooses not to use it to keep engagement high.

[HAUGEN] "Facebook knows that content that elicits an extreme reaction from you is more likely to get a click, a comment or a reshare..."

A Facebook spokeswoman disputed Haugen's knowledge of the company's inner workings... adding "We don't agree with her characterization of the many issues she testified about."

The Senate hearing reflects the rising anger in Congress with Facebook amid numerous demands for legislative reforms, with Senators warning that Facebook faces a reckoning akin to other industries like Big Tobacco.