And according to an European Union parliament source, around half the groups wanted an open hearing with the Committee on Civil Liberties, Justice and Home Affairs - with only a small majority of the Conference of Presidents agreeing to a closed meeting.
Mark Zuckerberg has agreed to meet with European parliament in private on May 22 in Brussels.
We've reached out to Facebook to ask why Zuckerberg will not take European parliamentarians questions in a public hearing.
Facebook CEO Mark Zuckerberg will cross the Atlantic and come to Europe to answer questions over the Cambridge Analytica data sharing scandal.
"Our citizens deserve a full and detailed explanation". Collins warned Zuckerberg last month that if he does not come voluntarily, he could be issued a formal summons, which would force him to appear before the parliament when he next enters the United Kingdom.
After appearing before the US Senate in April this year, the Facebook founder is all set to appear before the European parliament in a closed-door meeting to answer questions about the improper use of the personal data of millions of users by a political consultancy firm. Iran, Syria on agenda for Macron visit MORE (D-Del.) whether Bannon's goal "was to suppress voting or discourage certain individuals in the USA from voting".
"The founder and CEO of Facebook has accepted our invitation and will be in Brussels as soon as possible, hopefully already next week", he added.
That suggests he will avoid an uncomfortable public appearance and instead meet only with the legislature's top brass behind closed doors.
His concern and even frustration that the leadership of the EP agreed to hold a meeting behind closed doors, was expressed by a number of parliamentarians.
He might get tougher questions in Brussels, where an assertive new European data protection law comes into effect on May 25. "It must be a public hearing - why not a Facebook Live?" tweeted Guy Verhofstadt, a Belgian politician who is also a Brexit negotiator on behalf of the European Parliament.
The Digital, Culture, Media and Sport Committee said that Alexander Nix had accepted its summons.
Cambridge Analytica has denied doing paid work on the campaign for Brexit, and says its work on the Trump campaign did not use data at the centre of a Facebook scandal, where the details of around 87 million users were allegedly improperly obtained.