Politicians on two continents would love to know where Mark Zuckerberg is.

The Facebook CEO opened this year with a public mea culpa after the social media platform he nurtured into global dominance became entangled in congressional enquiries into Russian election meddling, with mounting evidence that Russian surrogates had used the platform to distort and divide.

Mr Zuckerberg had already walked back dismissing the notion that Facebook could be a vessel for political chicanery as “crazy”, and at the outset of 2018 he pledged to do better.

“Facebook has a lot of work to do – whether it’s protecting out community from abuse and hate, defending against interference by nation states, or making sure that time spent on Facebook is time well spent,” Mr Zuckerberg wrote in – what else – a Facebook post.

“My personal challenge for 2018 is to focus on fixing these important issues.”

Mr Zuckerberg was reminded of those words this week as his company again finds itself at the centre of a controversy over how the platform was exploited for political ends.

It has emerged that a firm employed by Donald Trump’s presidential campaign, Cambridge Analytica, harvested a vast repository of user data and used it to target voters.

The last time a political firestorm compelled Facebook to testify before Congress, Mr Zuckerberg sent a deputy. The same day the social media platform’s general counsel walked legislators through how malicious Russian-linked actors purchased ads and disseminated posts intended to fracture the American electorate, Mr Zuckerberg touted Facebook’s growth to investors on an earnings call.

This time, with a backlash rising in both America and the UK, politicians who are demanding answers want to hear them from Mr Zuckerberg himself.

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British Conservative MP Damian Collins wrote a letter to Mr Zuckerberg saying Facebook officials had “consistently understated” the risk of user data being taken without consent. No longer satisfied to question surrogates, Mr Collins sought to summon the CEO himself – and he called on Mr Zuckerberg to abide by his own resolution.

“It is now time to hear from a senior Facebook executive with the sufficient authority to give an accurate account of this catastrophic failure of process,” Mr Collins wrote.

“Given your commitment at the start of the New Year to ‘fixing’ Facebook, I hope that this representative will be you.”

Antonio Tajani, the President of the European Parliament, also called on Mr Zuckerberg to come and “clarify before the representatives of 500 million Europeans that personal data is not being used to manipulate democracy”.

On the other side of the Atlantic, a pair of US Senators – one a Democrat, one a Republican – asserted that Facebook knew about Cambridge Analytica sweeping in user data for years, but “failed to acknowledge it and take swift and meaningful action”.

They called for a hearing in which Mr Zuckerberg could help explain “whether Congress should take action to protect people’s private information”.

“Important questions also remain unanswered about the role of these technology companies in our democracy,” Minnesota Democrat Amy Klobuchar, and Louisiana Republican John Kennedy, wrote in a letter that also mentioned Twitter and Google, but “we have yet to hear from the leaders of these companies directly”.

Cambridge Analytica: Chris Wylie tells Channel 4 News data for 50 million Facebook profiles was obtained

In remarks to reporters, Senator Richard Blumenthal said Mr Zuckerberg “needs to testify under oath”, saying he “owes it to the American people” and suggesting the CEO should be subpoenaed.

An attempt by The Independent to speak to Mr Zuckerberg at Facebook’s Menlo Park headquarters was unsuccessful. A security guard informed a reporter who was broadcasting live that taking photos or video was prohibited.

A Facebook representative did not respond to a question about whether Mr Zuckerberg would testify before Parliament or Congress, saying only that the company intended to respond “by the given deadline” to Mr Collins.

“In the meantime, we continue to engage with the Committee and respond to their requests for information,” the representative said.

Facebook has been adamant that, insofar as any wrongdoing may have occurred, it is the fault of researcher Aleksandr Kogan (for passing data generated by an app survey to Cambridge Analytica), or Cambridge Analytica itself (for not destroying data when it said it had).

There has been no hack or breach, Facebook has said: only users willingly sharing their information, the type of consensual transaction that is the crux of the social media company’s business model.

“We are committed to vigorously enforcing our policies to protect people’s information. We will take whatever steps are required to see that this happens,” the company said in a statement.

But that looks unlikely to satisfy elected officials who are again invoking Facebook as an example of Big Tech’s transgressions. At the very least, they believe Facebook has been complicit in violating the privacy of users who did not understand what was happening.

“The troubling reporting on the ease with which Cambridge Analytica was able to exploit Facebook’s default privacy settings for profit and political gain,” Oregon senator Ron Wyden wrote in a letter to Mr Zuckerberg, “throws into question” both Facebook’s business model and “the role Facebook played in facilitating and permitting the covert collection and misuse of consumer information”.

As the fallout widens, Mr Zuckerberg’s public silence “is being felt”, said Sarah Roberts, an assistant professor of information studies at the University of California, Los Angeles.

“He needs to steer the ship through the crisis publicly,” Ms Roberts said, if nothing else to reassure jittery investors who just watched Facebook’s Wall Street value take its steepest single-day plunge in years.

But the larger task for Mr Zuckerberg and Facebook, Ms Roberts said, is explaining “the nature of Facebook” as a platform that is “intrinsically about monetisation of user data and behaviour”.