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Facebook co-founder Chris Hughes spoke out Friday against the social network's controversial policy regarding political ads.

The social network has faced intense criticism for its rules that allow politicians to make whatever claims they want -- true or untrue -- in ads that run on the platform. Last month, more than 250 Facebook employees signed an open letter to CEO Mark Zuckerberg condemning the policy.

"It's an abnegation of [Facebook's] responsibility to democracy," Hughes said at an event in San Francisco organized by the American Constitution Society, a progressive nonprofit. Hughes, who left Facebook in 2007, is one of the company's most outspoken critics, and an old friend and classmate of Zuckerberg.

During a speech at Georgetown University last month, Zuckerberg defended the policy by highlighting the social network's commitment to free speech and expression, versus the suppression of speech. But Hughes said the argument is a "misleading dichotomy."

Hughes was interviewed by Christine Pelosi, a Democratic political strategist and daughter of House Speaker Nancy Pelosi. She took issue with Facebook's decision not to take down a fake video of Nancy Pelosi that was altered to make it look like the house speaker was drunk. Hughes said Facebook shouldn't shy away from the challenge of determining what's true or not when it comes to political ads as well as organic content. "It's a fundamentally cynical viewpoint," he said. "They have made a name -- we made a name -- for ourselves by taking on hard problems."

Hughes' comments come as Facebook faces criticism on several fronts, including for data misuse, questions about election integrity, and misinformation. In the face of that blowback, Hughes has aggressively called for antitrust action against Facebook. In May, he published an op-ed in The New York Times calling for the breakup of the company he co-founded. Hughes argued Zuckerberg has too much control at Facebook, with a team that doesn't challenge his "unchecked power." So, Hughes says, government needs to hold him accountable.

Along with overseeing Facebook, Instagram and WhatsApp, Zuckerberg controls 60% of voting shares on Facebook's board, according to Hughes.

"We are a nation with a tradition of reining in monopolies, no matter how well-intentioned the leaders of these companies may be," Hughes wrote. "Mark's power is unprecedented and un-American."

In the past few months, Silicon Valley has faced a raft of renewed antitrust scrutiny. In September, New York Attorney General Letitia James announced a probe into Facebook. The investigation will focus on "Facebook's dominance in the industry and the potential anticompetitive conduct stemming from that dominance," James' office said in a statement at the time. So far, 47 attorneys general from around the nation have joined James' inquiry. The US Department of Justice is also opening a probe into Facebook, according to a September report by Reuters.

In his speech at Georgetown, Zuckerberg also reframed the story of Facebook's founding, saying it was partly a response to the Iraq War. On Friday, Hughes said he didn't know where that story came from. "I had no idea. It was new to me," he said. "I went to protests. I never went to a protest with Mark Zuckerberg."

Facebook didn't immediately respond to a request for comment.