WASHINGTON (Reuters) – Facebook Inc co-founder Chris Hughes on Thursday called for the world’s largest social media company to be split in three and said Chief Executive Mark Zuckerberg should be held responsible for privacy lapses.

Some U.S. lawmakers have also urged anti-trust action to break up big tech companies as well as federal privacy regulation. Facebook has been under scrutiny from regulators around the world over its data sharing practices and hate speech and misinformation on its networks.

“We are a nation with a tradition of reining in monopolies, no matter how well intentioned the leaders of these companies may be. Mark’s power is unprecedented and un-American,” Hughes wrote in an opinion piece in the New York Times on Thursday.

Facebook’s social network has more than 2 billion users across the world. It also owns WhatsApp, Messenger and Instagram, each used by more than 1 billion people. Facebook bought Instagram in 2012 and WhatsApp in 2014.

“The government must hold Mark accountable. For too long, lawmakers have marveled at Facebook’s explosive growth and overlooked their responsibility to ensure that Americans are protected and markets are competitive,” he said.

Facebook rejected Hughes’ call for WhatsApp and Instagram to be made into separate companies.

“Facebook accepts that with success comes accountability. But you don’t enforce accountability by calling for the break up of a successful American company,” said Facebook spokesman Nick Clegg in a statement.

“Accountability of tech companies can only be achieved through the painstaking introduction of new rules for the internet. That is exactly what Mark Zuckerberg has called for.”

Hughes, who is a former roommate of Zuckerberg, left Facebook in 2007 and then went to work for presidential candidate Barack Obama. Hughes, who bought and then sold the New Republic magazine, wrote a book last year about income inequality.

Hughes co-founded Facebook in 2004 at Harvard with the company’s Chief Executive Officer Zuckerberg and Dustin Moskovitz. He quit Facebook in 2007 and later said in a LinkedIn post that he made half a billion dollars for his three years of work.

“It’s been 15 years since I co-founded Facebook at Harvard, and I haven’t worked at the company in a decade. But I feel a sense of anger and responsibility.”

LAWMAKER PRESSURE RAMPS UP

Senator Elizabeth Warren, a Democratic presidential candidate, in March vowed to break up Facebook, Amazon.com Inc and Alphabet Inc’s Google if elected U.S. president to promote competition in the tech sector.

“Today’s big tech companies have too much power—over our economy, our society, & our democracy. They’ve bulldozed competition, used our private info for profit, hurt small businesses & stifled innovation. It’s time to #BreakUpBigTech,” Warren said on Twitter on Thursday.

Also on Thursday, U.S. Senator Richard Blumenthal, a Democrat, told CNBC he thinks Facebook needs to be broken up and that the Justice Department’s antitrust division needs to begin an investigation.

Representative Ro Khanna, a California Democrat, said in a statement he agreed that in retrospect that U.S. regulators “should not have approved Facebook’s acquisition of Instagram & WhatsApp in 2012.”

He said that “the way forward is to heavily scrutinize future mergers and to ensure no company has anti-competitive platform privileges.”

In one of a number of security and privacy scandals to hit the company, Facebook is accused of inappropriately sharing information belonging to 87 million users with the now-defunct British political consulting firm Cambridge Analytica.

The company has been in advanced talks with the U.S. Federal Trade Commission to settle a year-old investigation and said last month it expected to spend between $3 billion and $5 billion on a penalty.

On Monday, Republican and Democratic U.S. senators criticized reported plans for the settlement, calling on the FTC to impose harsher penalties and more restrictions on Facebook’s business practices.

Hughes said he last met with Zuckerberg in the summer of 2017, several months before the Cambridge Analytica scandal broke.

“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.

“And I’m worried that Mark has surrounded himself with a team that reinforces his beliefs instead of challenging them.”