Boris Johnson has been referred to police by the Cabinet Office over further potential rule breaches during the Covid pandemic.
The department said it made the referral after a review of documents ahead of the Covid public inquiry.
The former prime minister, who was fined last year for breaking Covid rules in 2020, denies any wrongdoing.
The Metropolitan Police said it was assessing information it had received from the Cabinet Office last week.
“It relates to potential breaches of the Health Protection Regulations between June 2020 and May 2021 at Downing Street,” the force added.
The Cabinet Office said officials had been obliged to disclose the documents to the police under civil service rules.
The Times, which first reported the story, says Mr Johnson has also been referred to Thames Valley police because his ministerial diary revealed visits by family and friends to Chequers – the prime minister’s country house in Buckinghamshire – during the pandemic.
Thames Valley Police said it had “received a report of potential breaches of the Health Protection Regulations between June 2020 and May 2021 at Chequers, Buckinghamshire”.
A spokesman for Mr Johnson said: “Some abbreviated entries in Mr Johnson’s official diary were queried by Cabinet Office during preparation for the Covid inquiry.
The spokesman added that Mr Johnson’s lawyers had written to the department, as well as the Commons Privileges Committee, “explaining that the events were lawful and were not breaches of any Covid regulations”.
The seven-member committee of MPs has been investigating whether Mr Johnson misled Parliament over Covid rule-breaking events in government buildings.
In a statement, the committee said it had received additional evidence from the government last week and asked Mr Johnson for a response, both of which it would now take into account during its probe.
Sources close to the former prime minister insist Mr Johnson has been advised by lawyers that all of these events were lawful and did not break any restrictions. They claim the referral to the police is politically motivated.
It is understood Mr Johnson has had no contact from the police.
The Cabinet Office said the material it had passed to police came from the “normal” process of reviewing documents to be submitted to the public inquiry into the government’s handling of the pandemic.
The public inquiry, which is separate to the privileges committee probe, will begin hearings next month.
A spokesperson for the Cabinet Office said: “In-line with obligations in the Civil Service Code, this material has been passed to the relevant authorities and it is now a matter for them.”
The BBC has been told the matter was not considered by ministers or the cabinet secretary, who heads the civil service.
Responding to the announcement, Labour’s deputy leader Angela Rayner said “These new allegations are for the police to examine but the government must explain who else knew at the time and why this has only now come to light.”
Liberal Democrat deputy leader Daisy Cooper, said Mr Johnson “should finally do one decent thing and consider his position as an MP”.
Lindsay Jackson, spokesperson for Covid-19 Bereaved Families for Justice, said Mr Johnson was “totally unfit for any form of public service, never mind being the prime minister”.
Mr Johnson resigned as prime minister last July, in part due to public anger over revelations he broke Covid lockdown rules.
In April 2021 he received a fine from the police for breaking lockdown rules after attending a gathering on his birthday in June 2020.
And, in May 2022, a report by then-senior civil servant Sue Gray set out a series of social events held by staff in Downing Street which broke the rules.
In October, following the short-lived premiership of Liz Truss, Mr Johnson joined the leadership race to replace her as Conservative leader and prime minister.
However, he later withdrew saying there needed to be a “united party in Parliament”.