Ministers have been ordered to hand over an unredacted cache of documents including Boris Johnson’s WhatsApp messages, notebooks and diaries to the Covid inquiry after losing a legal challenge. Government insiders said they would comply with the ruling by high court judges on Thursday, but were concerned that it would set a precedent for further demands for important documents and messages held by serving ministers. Bereaved families and opposition parties criticised the Cabinet Office’s failed judicial review, which sought to curb the powers of the inquiry chair, Heather Hallett, as a waste of time and money. Lord Justice Dingemans and Mr Justice Garnham, in their ruling, said the diaries and notebooks requested by Lady Hallett “were very likely to contain information about decision-making”. They described the terms of reference for the inquiry as “very wide” and suggested that Hallett’s team should be allow to “fish” for documents with an “informed but speculative request”. As a compromise, the judges decided that Hallett could see all the WhatsApps requested, but hand back those she deemed irrelevant without them being disclosed to third parties. A deadline of 4pm on Monday 10 July was set by Hallett for the Cabinet Office to hand over the unredacted batch of documents, which were initially requested on 28 April. The government said it would “fully comply”, but defended its decision to launch a judicial review to clarify Hallett’s powers under the 2005 Inquiries Act. Ministers had initially resisted handing over the full tranche of unredacted documents because of concerns that they contained private details, for example of a child’s schooling arrangements. Lawyers for the Cabinet Office argued during the one-day evidence hearing last Friday that Hallett’s request was “so broad” that it was “bound to catch” a large amount of material “unconnected” to Covid. Examples cited included WhatsApp messages held by a No 10 aide, Henry Cook, about one country invading another, and the trial of foreign nationals. But the inquiry’s lead counsel said the idea that the Cabinet Office could decide which documents were relevant “would emasculate this and future inquiries”. Johnson’s lawyer supported the inquiry, and warned that there was a “real danger” of undermining public confidence in the process if the Cabinet Office was successful. The ruling that means Hallett can hand back irrelevant material seemed to mollify their immediate concerns that private information may be shared with “core participants” in the inquiry, who are entitled to see certain evidence, speak in hearings and ask questions of witnesses. But government insiders still fear a precedent has been set that could lead to further demands for messages from serving ministers. The judicial review was criticised as “a desperate waste of time and money” by Deborah Doyle, a spokesperson for the Covid-19 Bereaved Families for Justice UK campaign group. She said: “The inquiry needs to get to the facts if the country is to learn lessons that will save lives in the future. That means it needs to be able to access all of the evidence, not just what the Cabinet Office wants it to see.” A successful inquiry could save thousands of lives in the event of another pandemic, she added. Labour accused the prime minister, Rishi Sunak, of “wasting time and taxpayers’ money” on “doomed legal battles”. Angela Rayner, the party’s deputy leader, called the high court ruling a “humiliating defeat”. She added: “The public deserve answers, not more attempts by the prime minister to undermine the Covid inquiry. There can be no more excuses for concealing the truth. It’s time to hand over the evidence.” A government spokesperson said the Cabinet Office was “cooperating in the spirit of candour and transparency” and that the inquiry was “an important step to learn lessons from the pandemic”. They said the judges had acknowledged that the judicial review was “valid as it raised issues … that have now been clarified”, and called the judgment “a sensible resolution” that would allow Hallett to see information she deemed relevant but still respect “the privacy of individuals”. The spokesperson added: “We will comply fully with this judgment and will now work with the inquiry team on the practical arrangements.” Emma Norris, deputy director at the Institute for Government, said it was “quite helpful” for the issue to have been settled early on in the inquiry process, given that it was likely to be a persistent feature in its later stages. “The use of WhatsApp in government decision-making is an area that’s receiving lots of attention,” she told the Guardian. “I’m sure the government will have had in mind not just the use of WhatsApp material in the Covid inquiry, but future ones, as well as broader considerations about how accessible government decision-making should be.”