Who does Mark Zuckerberg answer to? Facebook’s founder and CEO appeared before the US Senate this year to face questions about the Cambridge Analytica scandal, but he has refused similar requests from UK and Canadian lawmakers. Now, politicians from these two nations are banding together for a joint hearing on fake news and the internet, and they’re hoping that a united front will finally persuade Zuckerberg to attend.

In a letter to the Facebook chief signed by UK MP Damian Collins and Canadian MP Bob Zimmer, Zuckerberg has been asked to face questions from an “international grand committee on disinformation and fake news” at an event in London on November 27th.

“We would have thought that this responsibility is something that you would want to take up.”

“We understand that it is not possible to make yourself available to all parliaments,” write Collins and Zimmer. “However, we believe that your users in other countries need a line of accountability to your organization — directly, via yourself. We would have thought that this responsibility is something that you would want to take up.”

The letter notes that there have been no international committees examining Facebook’s role in spreading misinformation to date, despite the international impact of its platform. In recent years, the social media site has been implicated in fake news and election scandals of varying degrees of seriousness around the world, from the UK’s Brexit referendum to the 2016 US election and even the military-led genocide in Myanmar.

The hearing in the UK is being organized by a House of Commons select committee (the name for a group of MPs who work together to produce reports on specific topics). Calls for political action against Facebook and similar online platforms have been gaining traction in the country. Facebook has already been fined by the UK’s data watchdog, and earlier this week, the government outlined plans for a new “digital tax” on big tech companies.

Collins leads the UK’s Digital, Culture, Media and Sport Select Committee, while Zimmer heads Canada’s Committee on Access to Information, Privacy and Ethics. Zimmer will be flying to the UK to attend the hearing, which will go ahead regardless of Zuckerberg’s attendance. According to The Guardian, politicians from parliaments around the world who have failed to gain access to Zuckerberg will also be able to attend if they wish.

“Given your self-declared objective to ‘fix’ Facebook, and to prevent the platform’s malign use in world affairs and democratic process, we would like to give you the chance to appear at this hearing,” write Collins and Zimmer. “We both plan to issue final reports on this issue by the end of this December, 2018. The hearing of your evidence is now overdue, and urgent.”