Facebook executives said that a search for potential foreign interference in the two months before the British vote had not turned up any Russian advertising spending other than the three ads from the Russian entity. That company, known as the Internet Research Agency, has been identified by American intelligence agencies as the troll farm the Russian government used to influence the United States election.
The company did not disclose what steps it had taken in its internal review, and the British lawmaker who had requested the information accused Facebook of searching too narrowly. It remained possible that Russia found other ways to use Facebook or other social media to influence the referendum, known as Brexit.
Facebook, however, has been forthcoming about the extensive Russian use of its platform to try to influence elections in the United States and France, lending credibility to its assessment. Facebook’s statement also came days ahead of the release of a separate study from the Oxford Internet Institute concluding that Russia made little effort to influence the Brexit vote through other social media platforms, such as Twitter and YouTube.
“Over all, I think the Russian activity during Brexit seems to have been minimal,” said an author of the study, Philip Howard, a professor of internet studies at Oxford University and director of the institute, which studies online propaganda. “The real source of misinformation about the Brexit debate was homegrown.”
If confirmed, the Facebook statement and the Oxford study would upend the widespread presumptions of scholars and analysts that Russia must have meddled in the Brexit vote. Russia has long perceived the European Union as a regional rival, and its English-language propaganda outlets like Sputnik and RT pushed hard for the “leave” side in the referendum.
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So Russia’s apparent lack of interest in a covert social media campaign for Brexit like those it was simultaneously applying in the United States and elsewhere would be a puzzle.
Mr. Collins, the Conservative lawmaker, remained unconvinced by Facebook’s answer. He said in an email that he had asked Facebook for details about “any adverts and pages paid for or set up by Russian-linked accounts.” Mr. Collins said that Facebook had looked at only about 470 accounts and pages run by the Internet Research Agency, which had already been identified as active in the American election.
“It would appear that no work has been done by Facebook to look for Russian activity around the E.U. referendum, other than from funded advertisements from those accounts that had already been identified as part of the U.S. Senate’s investigation,” he said.
Facebook disputed that characterization of its search, which it said had been more extensive.
The company has told congressional committees that the Internet Research Agency spent more than $100,000 on ads that reached 126 million users in its effort to influence the American vote.
The Russian company posted roughly 80,000 pieces of divisive content that were shown to about 29 million people between January 2015 and August 2017, and those posts were liked, shared and followed by others — reaching tens of millions more people, Facebook said.
Facebook also said that it had found and deleted more than 170 accounts on its photo-sharing app, Instagram, that had posted about 120,000 pieces of Russia-linked content.
Facebook is by far the most widely used social media platform in Britain. But because the content of its pages is not publicly accessible, researchers seeking evidence of Russian interference in the Brexit vote have focused mainly on Twitter.
Twitter, in its own responses to congressional investigators, has identified 2,752 accounts linked to the Kremlin that were active around the American election.
A study reported last month by professors at the University of Edinburgh, in Scotland, found that 419 of those accounts had posted 3,500 times using Brexit hash tags. Although more than 70 percent of those posts took place after the vote, and thus too late to influence it, 38 of the accounts tweeted about Brexit a total of 400 times on the day of the vote.
A separate study, from the Swansea University, in Wales, found that more than 150,000 Russian-language Twitter accounts had posted tens of thousands of messages about Brexit in the days before the referendum. Upon closer inspection, however, most of those messages appear to be links to news articles.
The scholars who conducted both studies said that neither constituted conclusive evidence of a Kremlin campaign.