Mark Zuckerberg is in Brussels on the latest stop of his apology tour, delivering yet another mea culpa for privacy and policy blunders that led to one of the largest data leaks in Facebook's history and an unprecedented attack on democratic elections across the West.

Yes, it's as serious as all that.

The 34-year-old multibillionaire testified before the European Union's Parliament on Tuesday. Lawmakers discussed everything from Russian meddling in the 2016 US presidential election, which some argue handed a victory to Donald Trump, to the 87 million user profiles that were mistakenly shared with a now-defunct UK-based political consultancy called Cambridge Analytica.

"This represents an attack on our fundamental values," said European Parliament President Antonio Tajani on Tuesday. "We need to prevent this from happening again."

The twin scandals exploded onto front pages in March after The New York Times and Guardian's Observer publications exposed how Cambridge Analytica inappropriately gathered and used Facebook profile information and also influenced the "Leave" campaign during Britain's Brexit referendum.

Zuckerberg is now dealing with questions about whether you can trust him and the social platform he created 14 years ago. After being questioned for more than 10 hours over two days by the US Congress in April, Facebook's chief continues his efforts to reassure lawmakers, investors, advertisers and his 2.2 billion users that his company can be trusted with their data.

"We didn't take a broad enough view of our responsibility. That was a mistake and I'm sorry for it," Zuckerberg told the European Parliament Tuesday. "Advertisers and developers will never take priority over that as long as I'm running Facebook."

How Zuckerberg will fare with the EU is unclear. Zuckerberg escaped his hearings with both the US Senate and House of Representatives relatively unscathed -- that is, Facebook's shares actually rose during the hearings and then, two weeks later, the company reported earnings that topped Wall Street's expectations.

The EU representatives laid into him early in the hearing, asking a series of questions over 45 min before allowing Zuckerberg to answer them together.

One noted that Facebook had learned about Cambridge Analytica three years ago, but only admitted the leak recently. Another pointed to Facebook's pervasiveness of data collection. And others raised concerns about free speech allowing for Nazi propaganda.

"You have apologized 15 or 16 times in the last decade," said Guy Verhofstadt, a Belgian politician, before asking Zuckerberg whether Facebook will open its books to European regulators to consider whether his company is a monopoly. "It's not enough to say 'we're going to fix it ourselves.'"

Meanwhile, Nigel Farage who heads up Europe of Freedom and Direct Democracy, the European Parliament's right-wing populist group, asked Zuckerberg to defend the platform's political leanings and its transparency. Right-wing Facebook users who hold mainstream, not extremist political views "are being willfully discriminated against," he said.

"Would you accept that today Facebook is not a platform for all ideas that is operated impartially?" said Farage. "I'm not someone who calls for legislation on the international stage, but I'm starting to think that we need a social media bill of rights.

Zuckerberg insisted hate speech, terror and violence have "no place on our services." He added that his company is creating artificial intelligence tools to identify almost all the content from ISIS, for example. He also noted that Facebook is getting better at identifying bullying and possibilities of self harm.

"We'll never be perfect," Zuckerberg said in his response to the group. "Our adversaries, especially on the election side -- the people trying to interfere -- will have access to the same AI tools that we will. So it's an arms race, and we'll constantly be working to stay ahead."

Rebuilding trust

Zuckerberg still has a lot of convincing to do. So far, he has added new privacy controls that let people clear their web and app histories from Facebook, and he's promised that the 10,000 curators the company is hiring this year will clean up the fake news, hate speech and other objectionable content found on the social network.

Facebook's CEO told EU lawmakers Tuesday that the company will be adding 3,000 workers across 12 European cities as it doubles down on its fight against online abuse, hate speech and election interference. That hiring spree echoes Facebook's efforts in the US, where the social network promised to hire 10,000 new security and content moderation staffers by the end of 2018. Zuckerberg has said the hiring cost is necessary to address concerns that bad actors in Russia had used Facebook to spread propaganda and misinformation during the 2016 US presidential election. 

When he introduced a new dating feature for Facebook at the company's annual F8 developer conference last month, he was quick to add that it had designed with "privacy and safety in mind from the beginning."

Still, that hasn't been enough.

Some advertisers, including Firefox web browser maker Mozilla and speaker maker Sonos, stopped advertising on Facebook as the scandal was unfolding. And while users started a campaign called #DeleteFacebook, the company said it actually saw user growth during the three months ended March 31. And through it all, it turns out Facebook still pulled in money hand over fist -- counting nearly $5 billion in profits during that same time, a 63 percent increase over the previous year -- by using the details its users share to direct more relevant ads to them.

Even so, prominent tech executives, including Tesla CEO Elon Musk and Apple CEO Tim Cook, have criticized team Zuck. Musk, who deleted Tesla and SpaceX pages from Facebook, said the social network gave him "the willies." Cook said Facebook failed to regulate itself and vowed Apple wouldn't make money off its user's data.

When Zuckerberg faces lawmakers in Europe, he's going to be addressing regulators who take a much stronger stance on privacy than here in the US.

"It's clear now that we didn't do enough to prevent these tools from being used for harm," Zuckerberg said during his comments to Congress last month. "That goes for fake news, foreign interference in elections and hate speech, as well as developers and data privacy. We didn't take a broad enough view of our responsibility, and that was a big mistake."

CNET's Katie Collins, Rochelle Garner, Abrar Al-Heeti, Laura Hautala and Alfred Ng contributed to this report.

First published May 22 at 4 a.m. PT.
Update at 9:38 a.m. PT: Adds more details as event started.
Update at 9:38 a.m., 10:11 a.m. and 10:20 a.m. PT: Adds questions from European regulators.
Update at 10:30 a.m. PT: Adds Zuckerberg's answers to European regulators.

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