Six opposition leaders have written to Boris Johnson saying Dominic Cummings’ cross-country lockdown trip has “severely undermined” public health advice, and have demanded his dismissal. The Westminster leaders of the SNP, Liberal Democrats, Plaid Cymru, Green party, SDLP, and Alliance party of Northern Ireland, dispatched the joint letter after a meeting Tuesday morning. They said: “This is an issue that transcends politics. It has united people of every party and political persuasion, who believe strongly that it is now your responsibility as prime minister to return clarity and trust in public health messaging. We are clear that this can now only be achieved by removing Dominic Cummings from his post without further delay.” They pointed to comments from some of the government’s scientific advisers, warning that the actions of Cummings, the prime minister’s chief aide, risked undermining compliance with the coronavirus lockdown, and to polling suggesting the public believe he breached the rules. Cummings insisted on Sunday he had acted within the government guidelines. But in a snap YouGov poll published on Tuesday, 71% of respondents said they thought he had broken the rules, and 59% thought he should resign. Ian Blackford, of the SNP, said: “Boris Johnson must put his responsibilities to public health first and remove Dominic Cummings from post without further delay. The longer the prime minister takes to act the more damage will be done to trust in his government and the public health advice. That is not a price worth paying.” Ed Davey, the acting Lib Dem leader said: “The prime minister’s judgment has now become the issue, as this saga is confusing the vital public health messages needed to defeat coronavirus.” Separately, Jonathan Bartley, the co-leader of the Green party, is calling for the cabinet secretary, Mark Sedwill, to be asked to investigate whether the decision to allow Cummings to deliver his televised statement from the Downing Street rose garden breached the special advisers’ code of conduct. The code, which Cummings himself was involved in updating when Johnson became prime minister, says: “Special advisers must not take public part in political controversy, through any form of statement whether in speeches or letters to the press, or in books, social media, articles or leaflets.” The Labour leader, Sir Keir Starmer, had also been expected to attend the meeting of opposition leaders on Tuesday but in the event did not do so. Starmer responded to Cummings’ extraordinary Downing Street press statement on Monday by saying Johnson should have ordered an inquiry into the actions of Cummings, who drove more than 250 miles across the UK at a time when the public were being urged to stay at home. Starmer said: “This was a test of the prime minister and he has failed it.”