In a damning report, U.K. lawmakers Monday denounced Facebook for “intentionally and knowingly” violating data privacy laws, and called for a compulsory code of ethics to be imposed on social media companies.

The 108-page report on disinformation and “fake news” follows an 18-month investigation by the U.K. parliament’s Digital, Culture, Media and Sport Committee. The committee concluded that online companies have proved inadequate at self-regulation, and singled out Facebook chief executive Mark Zuckerberg for a “failure of leadership and personal responsibility.”

“The big tech companies are failing in the duty of care they owe to their users,” said Damian Collins, chair of the committee.

“The guiding principle of the ‘move fast and break things’ culture often seems to be that it is better to apologize than ask permission,” he added. “We need a radical shift in the balance of power between the platforms and the people. The age of inadequate self regulation must come to an end.”

The lawmakers urged parliament to impose a mandatory code of conduct on social media sites, and have them overseen by an independent regulator.

Facebook became a target of the inquiry after whistleblower Christopher Wylie revealed that data analysis firm Cambridge Analytica had illegally obtained access to millions of users’s data.

While Zuckerberg apologized over the privacy scandal, he refused to appear before British lawmakers, according to the report.

“By choosing not to appear before the Committee and by choosing not to respond personally to any of our invitations, Mark Zuckerberg has shown contempt towards both the UK Parliament and the ‘International Grand Committee’, involving members from nine legislatures from around the world,” the report said.

Globally, Facebook and other internet giants have come under increased fire for data privacy leaks and for their platforms’ roles in the spread of “fake news” and propaganda. In their report, the U.K. lawmakers described democracy as being under threat from hostile foreign actors seeking to sway elections and maliciously influence citizens through disinformation campaigns on social media.

Last month, Facebook said it wiped hundreds of Russia-linked pages, groups and accounts involved in a coordinated attempt to exert political influence outside the U.S. — the latest in a series of account purges. U.S. intelligence agencies have concluded that Russia used social media to meddle in the 2016 election.

Across Europe, regulators have called for probes into Facebook, which is being investigated in U.S. by the Federal Trade Commission.

“Mark Zuckerberg continually fails to show the levels of leadership and personal responsibility that should be expected from someone who sits at the top of one of the world’s biggest companies,” Collins said.

Facebook has not responded to the lawmakers’ comments.

Write to Hillary Leung at hillary.leung@time.com.