Damian Collins, the Conservative chairman of the committee, questioned Facebook’s findings, saying the company did not conduct a thorough search, something the company denied.

Facebook executives said 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.

Facebook did not disclose what steps it had taken in its internal review, and the British lawmaker who had requested the information accused the company 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.

Laura Cram, a political scientist at the University of Edinburgh who studies the internet, said the extent of Russian interference was impossible to assess without the public disclosure of a list of Kremlin-linked accounts active in Britain. “We don’t either have the evidence yet to say that there was no set of users that targeted Brexit or indeed the U.K. general election,” she said in an email.

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 before 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, like Twitter and YouTube.