Facebook is "unquestionably making hate worse", according to Frances Haugen.
The whistleblower made the statement in front of the Online Safety Bill committee in London, where British MPs have been considering what regulations they should impose on social networking platforms.
Frances said: "Facebook has been unwilling to accept even little slivers of profit being sacrificed for safety."
She also warned of the potential dangers of Instagram.
Frances explained: "Instagram is about social comparison and about bodies ... about people's lifestyles, and that's what ends up being worse for kids."
The UK is currently in the midst of introducing a law that will subject social media firms to checks by Ofcom, the media regulator.
And Frances has insisted she feels "incredibly proud of the UK for taking such a world-leading stance".
She added: "The UK has a tradition of leading policy in ways that are followed around the world.
"I can't imagine Mark [Zuckerberg, the CEO of Facebook] isn't paying attention to what you're doing."
Meanwhile, Frances observed that it's tough for Facebook employees to highlight their concerns.
She said: "When I worked on counter-espionage, I saw things where I was concerned about national security, and I had no idea how to escalate those because I didn't have faith in my chain of command at that point."
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