Downing Street staff were told to "clean up" their phones of messages about lockdown parties, the Independent reported.
The Information Commissioner's Office told Insider this could be a criminal offence.
Government lawyers face having to open an investigation into the allegation.
Downing Street staff who deleted messages about lockdown-breaking parties may have committed criminal offences, the Information Commissioner's Office (ICO) has warned.
Staff were "told to clean up their phone just in case," one source told the Independent, while another told the paper they were "told to get rid of anything that could look bad."
A senior member of staff made the instruction to Downing Street colleagues in early December after initial reports of parties in breach of lockdown restrictions, the Independent reported.
The ICO has warned that if such deletions were made, they could be criminal offences.
An ICO spokesperson told Insider: "Relevant information that exists in the private correspondence channels of public authorities should be available and included in responses to information requests received.
"Erasing, destroying or concealing information within scope of a Freedom of Information request, with the intention of preventing its disclosure is a criminal offence under section 77 of the Freedom of Information Act."
It is not clear if any Downing Street staff members have deleted messages, or if the Cabinet Office — the government department that includes 10 Downing Street — has received a Freedom of Information request.
Government lawyers may have to open investigation
Other legal requirements could force the Government Legal Department to open an investigation into the alleged instruction to delete messages.
Lawyers for Foxglove and The Citizens, two campaigning organisations bringing a judicial review against the government over the deletion of messages on WhatsApp, Signal, and other instant messaging services, wrote to the Government Legal Department following the Independent's report.
The lawyers said that if the Independent's story is true, then the Government is acting unlawfully in public law, under a separate section of the Freedom of Information Act regarding the retention of official records.
They argue that the Government Legal Department has a duty of candour as part of the ongoing judicial review process, and must find out if the requests for deletion were made and if so, when, and to disclose that information.
The opposition Labour party has said the deleted messages could also affect any subsequent investigations by the Metropolitan Police into the lockdown-breaching parties.
Emily Thornberry MP, Labour's shadow attorney-general, told Insider: "Boris Johnson told the House of Commons to respect the inquiry into his Downing Street parties, but now it has been revealed that his own staff may have broken the law to hide the truth from that inquiry, and any police investigations that may follow.
"It is one thing for Boris Johnson to try and defy political reality to cling on as Prime Minister, but it is another for his office to sanction breaking the law in order to help him do so. All evidence must immediately be preserved and handed over to the investigating authorities, so Boris Johnson and his staff can face the full consequences of their actions."
A spokesperson for the prime minister denied the Independent's report on Wednesday.
He told journalists: "It has been published what we've asked civil servants to do, which is to retain — should there be any — any requisite records. That's been clearly set out to all Number 10 staff."
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