Boris Johnson has been asked why he “sat on” the intelligence and security committee report on Russian interference in UK politics, during a fiery and acrimonious final PMQs session before parliament breaks for summer recess. Labour’s Keir Starmer said the report, completed last October, found Russia posed an immediate and urgent threat to national security, and he claimed Johnson deliberately suppressed the findings. “The prime minister received that report 10 months ago. Given that the threat is described as immediate and urgent, why did the prime minister sit on that report for so long?” he asked. Johnson said that as foreign secretary and now prime minister he had taken strong action against Russia, including expelling 153 Russian diplomats. He accused Starmer of “sitting on his hands” by supporting his predecessor Jeremy Corbyn’s Labour leadership, which he said had “parroted the line of the Kremlin” in the aftermath of the 2018 Salisbury poisonings. Starmer said he had personally condemned what happened in Salisbury and had supported the then prime minister, Theresa May. He said his commitment to national security could not be in doubt as in his pre-political career as director of public prosecutions he had worked on live operations with the security and intelligence services. “The report was very clear that until recently the government has badly underestimated the Russian threat,” he said. “The government’s taken its eye off the ball – arguably it wasn’t even on the pitch. After this government’s been in power for 10 years, how does the prime minister explain that?” Johnson claimed no country was more vigilant in protecting against Russian influence than the UK, and said new legislation was being introduced to protect critical national infrastructure and protect intellectual property. He said Starmer’s argument was that of an “Islingtonian remainer” who still did not accept the EU referendum result and tried to give the appearance that Russian interference was responsible for Brexit. Starmer said the delay had left a serious gap in the UK’s defences, and the threat from Russia deserved a far better response. Johnson said: “Everybody understands these criticisms are motivated by a desire to undermine the referendum on the European Union that took place in 2016, the result of which he simply cannot bring himself to accept.” Johnson has been severely criticised by opposition parties and the report’s author, Dominic Grieve, the former Conservative MP and former intelligence and security committee chair, for not allowing its release before the 2019 general election. It was finally published on Tuesday after the committee reconvened following a gap of more than six months following Tory party wrangling over who should chair it. Julian Lewis had the whip removed by the Tories after he was selected by committee members instead of Johnson’s choice, the former minister Chris Grayling.