Facebook Inc. Chief Executive Officer Mark Zuckerberg faces a clamor for answers from U.K. lawmakers following allegations a British firm that helped Donald Trump win the 2016 election kept information on tens of millions of the social network’s users.

Damian Collins, head of a U.K. parliament committee investigating the impact of social media on recent elections, asked Zuckerberg Tuesday to answer for a "catastrophic failure of process" as reports emerged concerning Cambridge Analytica, the U.K. firm at the center of the privacy scandal.

Separately, the EU Justice Commissioner Vera Jourova said she also plans to discuss the matter with Facebook during a visit in the U.S. this week.

“Reputationally, this seems catastrophic for Facebook, regardless of whether it is found to be innocent or not,” said Philip James, an attorney specializing in privacy and cyber security at law firm Sheridans in London. “No incident to date has resonated with both the public and government together so strongly.”

At issue is information on millions of Facebook users that Cambridge Analytica obtained from a researcher who shared the data without Facebook’s permission. According to published news reports, Cambridge University researcher Aleksandr Kogan created a personality-analysis app that was used by 270,000 Facebook users, who in turn gave the app permission to access data on themselves and their friends, ultimately exposing a network of 50 million.

‘Moving Aggressively’

Facebook said in a blog post on the issue that it was “moving aggressively to determine the accuracy of these claims. We remain committed to vigorously enforcing our policies to protect people’s information.”

U.K. Information Commissioner Elizabeth Denham said she’s in the process of obtaining a warrant to search Cambridge Analytica. Meanwhile, a panel of data privacy authorities from the 28-nation EU are expected to discuss the issue at a meeting in Brussels Tuesday.

Cambridge Analytica failed to respond to an access request by the U.K. Information Commissioner’s Office, forcing the authority to seek a warrant “to obtain information and access to systems and evidence,” it said in a statement on Tuesday.

The British company said in a statement that it’s been in touch with ICO since last year about various aspects of its activities. It said it remains “committed to helping the ICO and all other concerned organizations in their investigations and audits.”

Voluntary Search?

Concerning Facebook data, the firm said it “offered to share with the ICO all the information that it asked for and for the ICO to attend our office voluntarily, subject to our agreeing the scope of the inspection.”

In an earlier statement Cambridge Analytica said it “strongly” denied “false allegations” in the media and said that the Facebook data at the center of the scandal wasn’t used as part of services provided to the Trump campaign.

Facebook has enlisted the firm Stroz Friedberg to assess advertising-data provider Cambridge Analytica, whose handling of Facebook user data has mired the social networking company in controversy.

“On March 19, Facebook announced that it will stand down its search of Cambridge Analytica premises at the Information Commissioner’s request,” the ICO said in the statement. “Such a search would potentially compromise a regulatory investigation.”

Speaking to BBC Radio 4 on Tuesday, Denham said that the ICO was "concerned about the integrity of our investigation. We are also looking at Facebook at the same time. Our advice to Facebook was ‘back away.’” She told Channel 4 News earlier that the agency was seeking a warrant.

Kogan and Cambridge Analytica had agreed to be audited by Stroz Friedberg to determine whether the data company still has the disputed information.