The U.K. Parliament just threatened Mark Zuckerberg

Answer our questions, or else.

That’s basically what U.K. lawmakers are telling Mark Zuckerberg, in their strongest rebuke yet of the Facebook CEO, saying they’ll issue a formal summons if he continues to ignore their requests to come before parliament.

Damian Collins, chairman of the Digital, Culture, Media and Sport Committee, issued the ultimatum after Zuckerberg declined to answer U.K. lawmakers’ questions for the third time last month, sending a replacement in his place.

Last week Collins and his colleagues on the committee hammered Facebook CTO Mike Schroepfer on the details of the Cambridge Analytica scandal, its impact on the Brexit vote, and Facebook’s overall business model and how it influences the democratic process around the world.

Facebook is still reeling from the scandal revealed in March, where at least 87 million users’ profiles were harvested and used in targeted advertising during the U.S. elections in 2016.

But the committee was unhappy with the responses from Schropfer — which included 40 unanswered questions — and “lacked many of the important details” the committee required.

On Tuesday, Collins published a follow-up letter he sent to the company.

“It is worth noting that, while Mr. Zuckerberg does not normally come under the jurisdiction of the U.K. Parliament, he will do so the next time he enters the country,” Collins wrote, in a letter addressed to Facebook's head of public policy in the U.K. “We hope that he will respond positively to our request, but if not the Committee will resolve to issue a formal summons for him to appear when he is next in the UK.”

During last week’s hearing, Collins mentioned that Zuckerberg had confirmed his attendance in front of the European Parliament, but that report was unconfirmed and neither Brussels nor Facebook has since commented on the unconfirmed claim — which appears to stem from this Politico report.

Facebook has yet to respond to the threat of a formal summons against its CEO.

While Zuckerberg did agree to sit in front of Congress for 10 hours, many experts feel that the level of questioning was nowhere near as difficult as he would face in the House of Commons, where MPs were given much more time to drill down into the details than the five minutes afforded lawmakers on Capitol Hill.

Zuck should have a few things to say about data privacy in his keynote at the F8 developer conference in San Jose on Tuesday.

Cover image: Facebook CEO Mark Zuckerberg testifies before a House Energy and Commerce hearing on Capitol Hill in Washington, Wednesday, April 11, 2018, about the use of Facebook data to target American voters in the 2016 election and data privacy. (AP Photo/Andrew Harnik)