Ottawa and New York (CNN Business) Facebook's Mark Zuckerberg and Sheryl Sandberg did not attend a hearing in Ottawa on Tuesday, despite receiving summonses from the Canadian parliament.

The decision could result in the executives being held in contempt of parliament, the senior Canadian politician who sent the summons told CNN. The last time a member of the public was held in contempt by the parliament was 1913, according to the legislature's records.

Facebook instead sent two representatives from its public policy team to the hearing, which was tied to a gathering of an international committee examining Silicon Valley's impact on privacy and democracy.

Multiple lawmakers pointed out that Zuckerberg's failure to show up contradicted what he wrote in an op-ed in March when he wrote he was "looking forward to discussing them [online issues] with lawmakers around the world."

Bob Zimmer MP, the chair of the committee, slammed the executives for not attending.

"Shame on Mark Zuckerberg and shame on Sheryl Sandberg for not showing up today," he said toward the end of the meeting.

In a contentious exchange, British MP Damian Collins asked why Facebook had not removed a manipulated video of U.S. House Speaker Nancy Pelosi that went viral last week. Collins suggested that Facebook's refusal to remove the video was "irresponsible" and gave a "green light" to anyone to make false videos about politicians. YouTube removed the video.

Neil Potts, Facebook's director of public policy, said the company had downranked the video, meaning it will show up in fewer people's News Feeds.

Both Zuckerberg and Sandberg received formal requests from the Canadian Parliament earlier this month. Zuckerberg and Sandberg have testified before the United States Congress on the subject.

Zimmer said Monday night that Facebook had not told the committee whether its two most senior executives would be attending. He said committee members learned on CNN that Zuckerberg and Sandberg would not testify.

A Facebook spokesperson disputed that on Tuesday morning, saying the company had told the committee it would be sending Kevin Chan, its head of public policy for Facebook Canada, and Neil Potts, its director of public policy, to the meeting. The spokesperson added the company had been in ongoing communication with the committee.

Google and Twitter also sent representatives to address the committee, but the committee doesn't appear to have sent summons to those companies' top executives.

Lawmakers from at least ten countries, including the United Kingdom and Australia, were expected to attend the meeting, which is the second of its kind. The first meeting of the committee last year in London resulted in the release of secret internal Facebook documents.

"Collectively we represent about 450 million people, it's a bigger population group than the US," Zimmer, whose committee is hosting the international meeting, told CNN Monday.

Zimmer sent both Facebook executives summonses earlier this month. He said the company had submitted alternate names of people to attend in their place, but that he wants to hear directly from the social network's top two executives. Their presence is important, he said, because, "Knowing the structure of Facebook and how it is micro-managed right from the top, any change on the platform is done through Mr. Zuckerberg or through Ms. Sandberg."

"It's not that hard to jump on a plane and make some time to hear from legislators and answer their questions," he told CNN.

The decision to hold them in contempt, Zimmer said, would be voted on by the whole of Parliament.

"Nobody is going to come with some handcuffs and arrest them, but to be held in contempt by an entire country would not serve any platform well," he added.

Facebook FB spokesperson said in a statement earlier Monday: "Ultimately this is a decision for Parliament — we're not in a position to speculate. We share the Committee's desire to keep people safe and to hold companies like ours accountable. Right now we're focused on engaging in meaningful dialogue with the committee and look forward to answering their questions."

"We look forward to answering their questions and remain committed to working with world leaders, governments, and industry experts to address these complex issues," the spokesperson said.