Facebook faced another round of criticism and tough questions on election meddling Tuesday at a U.K. Parliament hearing with leaders from nine countries—and chief executive officer Mark Zuckerberg's chair was left empty.

Representatives from the U.K., Canada, Brazil, Latvia, Argentina, Ireland, Singapore, France and Belgium—which in total have more than 400 million constituents—grilled Facebook vice president of policy solutions Richard Allan on fake news, election interference and Zuckerberg's refusal to appear.

Allan, who was once a member of Parliament, admitted Zuckerberg's absence was “not great.”

“In this room we represent over 400 million people,” said Bob Zimmer, chair of the Standing Committee on Access to Information Privacy and Ethics in Canada's House of Commons. “And to not have your CEO sit in that chair there is an offense to all of us in this room, and really our citizens as well.”

Other leaders also expressed frustration and disappointment over Zuckerberg's empty chair, and repeatedly questioned whether Allan was the best representative to provide the answers they wanted to know. Charlie Angus, the vice-chair of the Canadian committee, said he was “deeply disappointed. The chair of Parliament's culture, media and sport select committee MP Damian Collins said he had hoped Allan's “boss might make a surprise appearance.”

Allan said that he volunteered to represent Facebook in the hearing because he has closely followed content moderation policy debates and changes in Singapore and Ireland, which had representatives present Tuesday.

International leaders also pressed Allan on information found in documents seized by Parliament last week from the founder of U.S. software company Six4Three. The Guardian reported that the documents allegedly contained emails between Zuckerberg and other senior executives related to the Cambridge Analytica scandal.

Collins said that the documents allege “an engineer at Facebook notified the company in October 2014 that entities with Russian IP addresses have been using a Pinterest API key to pull over 3 billion data points a day.”

“Was that reported or was that just kept … within the family and not talked about?” Collins asked.

Allan responded that the emails' information was at “best partial and at worst potentially misleading” and that he would follow up with a clearer answer on what steps Facebook took.

He also faced questions on whether Facebook white-listed apps that paid large sums for advertising, granting them more access to user data, and retaliated against those that didn't. Allan said he doesn't believe that happened but again promised to return with a more certain answer.

Representatives from Latvia and Singapore pressed Allan on whether Facebook would protect democracy in smaller countries elections, and Argentina and Brazil's representatives asked whether Facebook subsidiary WhatsApp would also be moderated to prevent election interference.

Angus closed out Allan's portion of the Tuesday hearing with calls to not just regulate the “symptoms” of Facebook, which he described as fake news and hate speech, but rather to regulate the company as a whole. He said consumers who want to leave the platform are left with the choices of WhatsApp or Instagram—which are owned by Facebook—and that perhaps the best next regulatory step would be an antitrust case.

“I'm saying that perhaps Facebook, in it's unwillingness to actually be accountable to the international body and legislators around the world, that maybe antitrust would be something that would help us be able to make sure that we get credible democratic responses from a corporation,” Angus said.