"I say that specifically because it was only two weeks ago that Mark Zuckerberg decided that Facebook is not going to censor politicians that are spreading disinformation, weaponizing racial hatred and even using voter suppression tactics," argued Kaiser, whose memoir, "Targeted," was released Tuesday .

"Facebook is actually the biggest threat to our democracy, not just foreign actors," Kaiser said on " Closing Bell ."

Facebook 's approach to political advertising shows why it presents a serious risk to American democracy, Cambridge Analytica whistleblower Brittany Kaiser told CNBC on Tuesday.

Brittany Kaiser, former employee of Cambridge Analytica, near the Capitol building in Washington, DC.

Earlier this month, Facebook said it would not prevent President Donald Trump's re-election campaign from running an ad with false claims about former Vice President Joe Biden and his son. CNN rejected the ad for making a "demonstrably false" narrative about Biden, whose campaign had asked Facebook to also remove the ad.

In September, as the 2020 U.S. presidential election approaches, Facebook said it will not fact-check or remove content posted by politicians even if it is in violation of the company's rules.

Facebook did not immediately respond to a request for comment on Kaiser's remarks.

Kaiser is a former director at Cambridge Analytica who came forward to The Guardian in March 2018 to share information on the practices of the now-defunct political consulting firm. She left the company after a few years of work in January 2018.

Kaiser's disclosure came shortly after a different whistleblower stepped forward with information, igniting a scandal that brought down Cambridge Analytica and resulted in the Federal Trade Commission fining Facebook, 15 months later, $5 billion for mishandling data.

Facebook said Cambridge Analytica improperly obtained data of up to 87 million of its users who took a personality test through a third-party app — the app not only gathered the users' Facebook data, but also gathered data on their Facebook friends. Cambridge Analytica worked for the 2016 Republican presidential campaigns of both Donald Trump and Sen. Ted Cruz of Texas.

Last week, Zuckerberg said he considered banning all political advertising from Facebook, but decided against it.

"I believe that when it's not absolutely clear what to do, we should err on the side of greater expression," the CEO said in a speech delivered at Georgetown University.

But Facebook said on Monday it is taking further steps to combat disinformation on its platform.

Those steps include the display of additional information about the confirmed owner of a Facebook page, plus better labeling of content that independent fact-checkers have deemed to be incorrect.