Fresh questions are being raised over whether Rishi Sunak has handed over all relevant material to the Covid inquiry after reports that pranksters have been able to access an old phone number he used during his time as chancellor. The prime minister will face a day of questioning at the inquiry on Monday, where he is expected to be questioned about his claims that scientists had too much power. He will also be asked detailed questions about the “eat out to help out” scheme that many experts believe allowed the virus to spread. However, he is also set to be confronted over his claims that he could not deliver WhatsApp messages covering a crucial period because he had changed phones several times and the messages had not been backed up. There have subsequently been reports that pranksters were able to access a longstanding phone number for Sunak, which rang before playing a voicemail recording. Questions are now being asked over whether Sunak has handed the inquiry access to material associated with that number. Missing messages have already been the subject of scrutiny at the inquiry as a result of a huge cache that former prime minister Boris Johnson was unable to hand over. Johnson said he had been unable to access messages between 31 January and 7 June 2020 – a crucial period in the pandemic. The inquiry heard that about 5,000 WhatsApp messages from the period from Johnson’s phone had not been located. Asked about the missing WhatsApps, Johnson said: “I don’t know the exact reason, but it looks as though it’s something to do with the app going down and then coming up again, but somehow automatically erasing all the things between that date when it went down and the moment when it was last backed up.” The Lib Dems have written to Victoria Prentis, the attorney general, asking her to clarify the status of Sunak’s phones and messages. She has been asked if the messages are accessible, with the warning that it “would be a criminal offence under the Inquiries Act 2005” to withhold them. The letter asked what legal advice had been provided to Sunak on the requirements under the Inquiries Act, and whether the government received any contact from the police regarding potential breaches. “It is a travesty that Rishi Sunak’s WhatsApp messages have not been released to the Covid-19 inquiry,” said Daisy Cooper, the Lib Dem deputy leader. “The allegations that Sunak’s ‘broken phone’ may be recoverable will be highly concerning to the thousands of bereaved families who lost loved ones during the pandemic. “Sunak must not duck and dive from scrutiny and accountability over his decisions during the pandemic. Any such action would certainly be immoral – and possibly illegal. The prime minister must come clean. If he has nothing to hide, he has nothing to fear.” A government spokesperson said: “As a matter of longstanding policy, we would never comment on security matters. The prime minister and government is fully cooperating with the inquiry. We have submitted more than 55,000 documents in support of their work. We are clear that to ensure the integrity of the inquiry, evidence submitted should be heard in context and in full.” In his witness statement to the inquiry, Sunak said: “Having changed my phone a number of times over the last three years, I do not have access to the WhatsApp messages that I sent or received during the relevant time, and neither were the messages backed up. “My expectation would be that, if the officials on those groups had considered that any information being communicated by WhatsApp message needed to be preserved to form part of the official HMT record, then those officials would have taken steps to ensure that happened.”