MI5 chief Sir Ken McCallum acknowledged Russian interference in the 2016 Brexit referendum but cautioned against overstating its impact, marking a public divergence from Prime Minister Andy Burnham's recent claims about Moscow's role in the vote.
McCallum said it was "a matter of public record" that Russian interference occurred through online trolls and bots, as well as Russian state media outlets like Russia Today and Sputnik operating around the referendum. However, he warned that characterizing these efforts as consequential played into adversaries' hands.
"There is a really important difference between interference attempted and outcome swayed," McCallum said in remarks after his annual speech at MI5's London headquarters. He expressed concern that publicizing Russian trolls would make their efforts appear more effective than they were, saying the accounts would be "delighted" to receive front page coverage "despite the comparative unimpressiveness" of their activities.
Burnham told The Rest is Politics podcast on Monday that upon taking office he had asked security officials about Russian interference in 2016 and received "the clear answer that, yes, there was." A No 10 spokesperson later clarified that while the prime minister believed it was highly likely Russia attempted to influence the referendum, he did not believe those efforts succeeded. Burnham denied he was implying the referendum result was illegitimate because of Russian activities.
Conservative deputy leader Alex Burghart called McCallum's remarks "an extraordinary slap down to the prime minister." Reform UK leader Nigel Farage accused Burnham of lying, asserting there was "no Russian interference." Former Prime Minister Boris Johnson said security services told him in 2016 that there was "no evidence of any successful interference in the 2016 referendum, by Russia or any other power."
McCallum agreed the prime minister was correct that Russia conducted a hack and leak operation during the 2019 general election campaign. A 2020 parliamentary report did not reach a firm conclusion on whether Russia had attempted to intervene in UK elections and referendums, but it criticized the government for failing to fully assess and counter Russian troll accounts on social media.