Facebook co-founder Chris Hughes has called for the breakup of the company, which counts Instagram, Messenger, and WhatsApp as part of its social media empire.

In an opinion piece in the New York Times, Hughes said his fellow co-founder, Mark Zuckerberg, had built an “unprecedented and un-American” monopoly of power.

Facebook currently has 2 billion users alone, while WhatsApp, Messenger, and Instagram count have more 1 billion subscribers.

Hughes co-founded Facebook in 2004 while at Harvard with Zuckerberg and Dustin Moskovitz. He quit, however, in 2007 to work as a strategist for then-presidential candidate Barack Obama in 2008.

“Mark is a good, kind person. But I’m angry that his focus on growth led him to sacrifice security and civility for clicks,” Hughes said, adding that Zuckerberg is surrounded by a team of people that reinforce his opinion rather than speaking true-to-power.