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LONDON — British parliamentarians said Tuesday that they were prepared to issue a formal summons for Facebook Chief Executive Mark Zuckerberg to appear before them and answer questions over a data scandal which has engulfed the technology giant.

The social network has faced questions on both sides of the Atlantic over how millions of users' details got into the hands of political consultancy Cambridge Analytica, and over its wider handling of personal data.

Zuckerberg previously declined to come in person to answer questions from British lawmakers, instead sending Facebook's Chief Technology Officer Mike Schroepfer to face a four-hour grilling last month. Schroepfer apologized for errors made by the firm and vowed to do more to improve transparency.

But the head of parliament's Digital, Culture, Media and Sport Committee Damian Collins said on Tuesday he still wanted Zuckerberg to appear before lawmakers, ideally by May 24, and listed 39 questions or points which remained unanswered.

Collins noted that Zuckerberg was already reportedly planning to speak to the European Parliament in May.

"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 his letter.

"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 U.K."