Keir Starmer is under police investigation over claims he broke lockdown rules by having a beer and takeaway with staff during election campaigning last year, after Durham constabulary said they had received “significant new information” about the gathering. While Labour said it was happy to cooperate with Durham police and insisted no rules were broken, the news is deeply uncomfortable for the party leader, who had called for Boris Johnson to resign when he was investigated for a breach of the law. Following significant pressure from some newspapers and Conservative MPs to look again at events in Durham, the force said in a statement it had opened an inquiry. The announcement was timed to follow the end of local election campaigning and voting, it said. “Earlier this year, Durham constabulary carried out an assessment as to whether Covid-19 regulations had been breached at a gathering in Durham City on 30 April 2021,” the statement said. “At that time, it was concluded that no offence had been established and therefore no further action would be taken. Following the receipt of significant new information over recent days, Durham constabulary has reviewed that position and now, following the conclusion of the pre-election period, we can confirm that an investigation into potential breaches of Covid regulations relating to this gathering is now being conducted.” It remains unclear what new information has been given to the police. The local Labour party organised a quiz for activists the same evening but Labour sources said this was held on Zoom and Starmer had nothing to do with the event. Other recent newspaper coverage has focused on the amount of takeaway food ordered and Labour’s admission that it mistakenly said Angela Rayner, the deputy leader, was not at the event. A Labour party spokesperson said: “We’re obviously happy to answer any questions there are and we remain clear that no rules were broken.” One complication for Starmer is that the Labour leader not only called for Johnson to step down as prime minister after he was fined for breaking lockdown rules, but did so as soon as the Metropolitan police began investigating alleged breaches in Downing Street, saying the prime minister should “do the decent thing and resign”. Asked on Friday about Starmer’s previous comments, the shadow attorney general, Emily Thornberry, told the BBC the resignation call had been because Johnson had misled parliament about the parties and thus the situations were different. The Durham police inquiry will examine, among other information, video footage showing Starmer holding a bottle of beer inside the constituency office of the City of Durham MP, Mary Foy, during the byelection campaign for the nearby Hartlepool seat. Campaigning was allowed at the time, and the investigation will centre on whether the gathering was reasonably necessary for work-based purposes, as was set out in Covid regulations. Durham police said in 2020, responding to anger over Dominic Cummings’ travels to the county, that they did not issue fines retrospectively. The Met, which covers London, has been issuing fixed-penalty notices for past breaches against Johnson and others. In addition to Johnson, the chancellor, Rishi Sunak, and dozens of officials have been fined for breaking Covid rules, and could potentially face more penalties over other events. In a TV clip on Friday, Starmer said he was “confident there was no breach of the rules”. “I was working, I stopped for something to eat. No party, no breach of the rules,” he said. “The police, obviously, have got their job to do, we should let them get on with it, but I’m confident that no rules were broken.” Thornberry said Labour would “answer whatever questions are put to us and we’ll do everything that we can to help”. “But we’re completely confident that no rules have been broken,” she added. “It’s fine. I appreciate they’ve been put under a lot of pressure – there’s lots of people who’ve been campaigning for the police to open this investigation; lots of Conservative MPs have been asking about it; lots of the Conservative-supporting newspapers have been making a big fuss about it.” Richard Holden, the Tory MP for North West Durham, who has been among those leading calls for a police inquiry, said the force was doing “exactly the right thing”. He said: “It’s vital that the man who wants to be prime minister is held to the same standard as the prime minister and everybody else.” Labour’s defence has been that the takeaway was necessary for campaign staff, who carried on working while eating. However, reports have questioned the volume of food and alcohol supplied as well as Labour’s claim that there were no other options for dinner. Starmer said the food had been ordered as the staff prepared an online event for members. “In Durham, all restaurants and pubs were closed, so takeaways really were the only way you could eat. So this was brought in and at various points people went through to the kitchen and had something to eat, and got on with their work,” he said.