England’s chief nurse has confirmed she was dropped from the Downing Street daily coronavirus briefing after refusing to back Dominic Cummings. Ruth May said that in a trial run for the 1 June briefing, she was asked about Boris Johnson’s chief adviser’s decision to drive his family from London to Durham during lockdown while his wife had suspected Covid-19. After she failed to back Cummings, she said, she was told she was no longer needed for the televised press conference taking place later that day, and she was never given an explanation why. Ministers and No 10 have denied reports that May was stood down over Cummings. Aides to the prime minister briefed journalists at the time that she may not have made it to the briefing because she could have been stuck in traffic. Appearing before MPs on the House of Commons public accounts committee on Monday, May said she had attended preparations for the briefing and was told she was no longer needed, without explanation. “It is indeed true I was dropped from the briefing, but that happened to many of my colleagues as well,” she said. Asked if she was questioned in a trial run before the briefing about her views on Cummings’ behaviour during lockdown, May said: “We talk about lots of these preparations questions and of course I was asked about lockdown and rules to lockdown.” Asked by the committee chair, Meg Hillier, for her views on Cummings’ behaviour and whether it was a breach of the rules, May said: “In my opinion the rules were clear. They were there for everyone’s safety and they applied to us all.” She added: “I don’t know why I was dropped from the briefing, you would have to ask other people.” In May’s absence on 1 June, the health secretary, Matt Hancock, presented the daily slides on Covid-19 alongside Prof John Newton from Public Health England. Appearing before the Commons on Monday, Hancock was asked by his Labour shadow, Jonathan Ashworth: “Did he really acquiesce in the silencing of the chief nursing officer at the height of this pandemic?” Hancock did not respond to the question. On 12 June, Grant Shapps, the transport secretary, told the daily briefing that May had not been blocked from attending. He said: “I don’t think it is true,” before adding that he was “sure she’ll be back here again”. Scientific and medical experts who appeared at other briefings alongside a politician were initially reluctant to get involved in the row surrounding Cummings, who while in Durham also made a 60-mile round trip to a beauty spot, which he said was to test his eyesight before a longer journey back to London. On 28 May, Johnson tried to prevent the chief medical officer for England, Prof Chris Whitty, and the chief scientific adviser, Sir Patrick Vallance, from answering questions on the subject, before Whitty said that neither he nor Vallance wished to comment on politics. However, on 30 May, England’s deputy chief medical officer, Jonathan Van-Tam, caused embarrassment for the government by saying, in response to a question about the alleged lockdown breach: “In my opinion the rules are clear and they have always been clear. In my opinion they are for the benefit of all. In my opinion they apply to all.” Responding to May’s comments, Layla Moran, the Liberal Democrat leadership candidate, said the incident suggested ministers were “happy to silence the science when it suits them”. Downing Street has not responded to a request for comment.