The chair of the UK Covid-19 public inquiry may have to resign if the government succeeds in its high court attempt to block the unredacted disclosure of ministers’ WhatsApp messages, the lawyer representing thousands of bereaved families has said. Elkan Abrahamson, who represents the Covid-19 Bereaved Families for Justice group, which is a core participant at the inquiry, said the dispute between the government and the inquiry over texts and other documents had become “an existential struggle”. He said if the inquiry did not receive the potential evidence “the only logical response of the chair is to resign because she can’t properly do her job”. The intervention increases pressure on Rishi Sunak to back down in the power struggle over an inquiry that was set up by a government in which he was a senior member. It shows the inquiry risks losing the support of thousands of bereaved people if the government’s case succeeds. On Tuesday, the chair, Heather Hallett, is expected to address the Cabinet Office’s decision to seek a judicial review of her demand for the texts stored on phones owned by Boris Johnson and one of his advisers, as well as the former prime minister’s notebooks. The government has said much of the material is “unambiguously irrelevant”, amid fears it could open the door for wider disclosure of senior politicians’ messages, but Lady Hallett argues its relevance is for her to decide. The inquiry declined to comment on Abrahamson’s view. The lawyer was speaking at a press conference in central London where unions and the bereaved demanded the effects of austerity since 2010 be investigated in the three-year inquiry. Some participants are concerned the inquiry may not have allocated sufficient time to cross-examine the then prime minister, David Cameron, and the chancellor at the time, George Osborne, on issues such as funding of the NHS, welfare and social care in the years before the pandemic. Abrahamson’s call for Hallett to consider quitting was backed by Lobby Akinnola, whose 60-year-old father died with Covid in April 2020. “If the court finds against the inquiry, it is effectively rendering the inquiry lame,” he said. “She has made it clear she is committed to do a good inquiry [and] ... I would fully understand her saying if she can’t do it then she won’t do it.” Children’s charities have attacked the inquiry for making “no provision to hear from children who lost access to play, seeing their friends and education”. Save the Children UK, Just for Kids Law and the Children’s Rights Alliance for England said the inquiry’s promised “listening exercise” had not made it clear how children would be included. An online form for people to share their experiences excludes those aged under 18, “which potentially denies 14 million children from having their say”, the charities said. In May 2022, Hallett widened the terms of reference to include “children and young people, including the impact on health, wellbeing and social care education and early years provision”. Taking evidence directly from children is not yet on the cards, partly because of the significant increase in safeguarding required, although the inquiry has not ruled it out. The inquiry said it was developing the best ways for under-18s to engage with the inquiry safely and in an appropriate format, taking advice from experts in child protection.