MI5 director-general Ken McCallum has confirmed that Russia attempted to interfere in the 2016 Brexit referendum but warned against overstating the impact of those efforts on the result. The British PM, though, refused to back down.
Speaking after his annual threat assessment at MI5’s Thames House headquarters on October 13, McCallum said it was “a matter of public record” that Russian State-backed outlets such as Russia Today (RT) and Sputnik, along with online trolls and bots, sought to influence the campaign.
He stressed, though, that there was “a really important difference between interference attempted and outcome swayed”.
“I am a little bit anxious that we don’t play into our adversaries’ hands by making these trolls look 10ft tall,” he added.
Continuing the debate for several more days, he suggested, would simply delight Russian trolls who “didn’t appear to do all that much” and whose efforts had shown “comparative unimpressiveness”.
The campaign group 89up has calculated that RT and Sputnik between them published 261 misleading articles in the run-up to the vote, with a potential reach of 134 million page impressions.
The remarks followed comments by Prime Minister Andy Burnham on the Rest is Politics podcast, in which he said that upon entering Downing Street he had asked whether Russia interfered in the 2016 vote and received “the clear answer that, yes, there was”.
Burnham later told the House of Commons that the referendum result itself was not in dispute and denied suggestions he was questioning its legitimacy.
On October 14, though, Burnham told parliament during Prime Minister’s Questions, after being grilled by the opposition, that Britain must be “clear-eyed about what happened in the past” and there was “incontrovertible evidence” of interference in the UK’s democratic processes.
Conservative leader Kemi Badenoch had accused him of “doing Russia’s dirty work” and asked whether he agreed with the MI5 director-general that talking up Russian interference had been a mistake. “You can’t fight misinformation with misinformation,” she said.
Burnham did not answer the question directly, asking instead whether Badenoch had read the Russia report published by parliament’s Intelligence and Security Committee in July 2020, which found that the British Government had neither seen nor sought evidence of successful Russian interference in the referendum.
Conservative deputy leader Alex Burghart described McCallum’s intervention as “an extraordinary slap down to the prime minister”.
McCallum also noted a confirmed Russian “hack and leak” attempt during the 2019 general election campaign, when classified papers on UK-US trade talks were put online weeks before polling day.
In his broader threat assessment he described Russia as “aggressor number one”, while stating that its conventional intelligence capabilities had been significantly reduced by the expulsion of nearly 1,000 officials from embassies since the invasion of Ukraine, forcing greater reliance on criminal proxies and other non-traditional methods.
MI5 is devoting more resources to hostile states than at any point in the Cold War, he said, with state-based threats having quadrupled over the past decade.
Former prime minister Boris Johnson said in a post on X that when he became foreign secretary in July 2016, the security services told him there was “no evidence of any successful interference in the 2016 referendum, by Russia or any other power”.
He added: “Either the security services have changed their view, which would be very odd, or Burnham is lying about what he has been told.”
Nigel Farage, leader of Reform UK, called Burnham “a liar” and stated there was “no Russian interference” in the referendum, speaking at a press conference in Dover on October 12. He referred to the same briefing Johnson had received as foreign secretary and described Burnham’s comments as “outrageous”.
Shadow communities secretary Katie Lam accused Burnham of peddling “conspiracy theories”.
Former Brexit secretary David Davis characterised the prime minister’s approach as “performative, not real”, suggesting that as mayor of Greater Manchester he had been able to make such claims without serious challenge.
The pro-Brexit group Britain Unbound called Burnham’s comments “another crude attempt to undermine the legitimacy of the decision that the British people made in 2016”, adding that while foreign interference was unacceptable, there was “no good reason to believe that Russian intervention influenced the outcome” and that it was “insulting to suggest that voters were so easily duped”.
Foreign Office minister Stephen Doughty reiterated Burnham’s line on Russian interference in a Sky News interview on October 12, citing security minister Dan Jarvis’s assessment that Moscow had attempted to interfere but had not succeeded. Pressed for specifics, he did not set out the evidence underpinning the claim.
This was one of the most PAINFUL CAR CRASH interviews you’ll ever see with Labour foreign minister Stephen Doughty on @GMB about Andy Burnham saying Russia interfered in the Brexit referendum.
Susanna Reid grows increasingly frustrated as he refuses to answer her questions, and… pic.twitter.com/yNOI3hqQ5x
— J Stewart (@triffic_stuff_) October 13, 2026
