Boris Johnson is weathering allegations of parties within No 10 during Covid restrictions
The Metropolitan Police has referred itself to the police watchdog over a complaint suggesting its handling of allegations of a party at Downing Street last Christmas could amount to "aiding and abetting a criminal offence".
In her letter, sent the day before leaked footage showed No 10 staff joking about potential media questions about an alleged event on 18 December last year, Baroness Jones of Moulsecoomb criticised Commissioner Dame Cressida Dick's "refusal" to investigate the allegations.
The Green Party peer also argued that due to the "extensive" police presence in Downing Street, there is a "case to answer" for the force "aiding and abetting a criminal offence, or deliberately failing to enforce the law in favour of government politicians and their staff".
In a letter to the Green Party on Tuesday, Scotland Yard said her complaint had been split into two parts - one of which it had referred to the Independent Office for Police Conduct (IOPC), and the other to the London Mayor's Office for Policing And Crime (MOPAC).
"I have referred your complaint to the Independent Office for Police Conduct given that you effectively allege misconduct in public office by MPS police officers," said the Met's directorate of professional standards, Acting Detective Chief Superintendent Tony O'Sullivan.
"The IOPC will now make a determination as to whether the complaint needs to be investigated and if so, how."
The watchdog's decision will be made by the end of the week, if not sooner, The Independent understands.
Confirming that the IOPC had received the Met's self-referral, a spokesperson said: "We are assessing it to determine what, if any, further action may be required from us."
The watchdog will likely assess to what extent Baroness Jones herself has been personally affected by the matter while considering how to respond to her complaint.
A Met inspector said the second part relates to Lady Jones's complaint regarding Dame Cressida, adding: "The Metropolitan Police Service is not the appropriate authority to handle complaints about the commissioner and, as such, this has been referred to MOPAC."
In her complaint, Lady Jones claimed Dame Cressida's "refusal" to investigate could amount to "a conflict of interest and a potential coverup" - arguing that police "must" have known of the event if it took place due to their "extensive presence" at No 10, "including their role in controlling all access to and from" the building.
Former No 10 communications director Alastair Campbell, who worked in Tony Blair's government, has also since questioned whether it is possible that police officers - and the prime minister - would not have been aware of such an event taking place within the building.
But Conservative chief whip Mark Spencer has argued that "no single person could account for what's happening in those buildings - they are huge buildings", with "hundreds and hundreds of offices and rooms".
It is alleged that the event last December, at a time when London was under Tier 3 Covid restrictions, saw officials and advisers make speeches, enjoy a cheese board, drink together and exchange Secret Santa gifts - although the prime minister is not thought to have attended.
Shortly after the allegations were first printed in the Daily Mirror, Mr Johnson's former press secretary Allegra Stratton quit her government role in response to leaked footage of her joking about the alleged incident with fellow aides at a mock press conference last December.
In a statement the day after Ms Stratton's resignation - and after Lady Jones's complaint - Scotland Yard said it would not investigate the matter, but said that any evidence gathered by an internal government inquiry would be passed to the force for consideration.
"The correspondence and footage does not provide evidence of a breach of the health protection regulations but restates allegations made in the media," the statement said. "Based on the absence of evidence and in line with our policy not to investigate retrospective breaches of such regulations, the Met will not commence investigation."
Cabinet secretary Simon Case last week "recused" himself from leading the government's internal inquiry after The Independent and other outlets reported allegations of an impromptu drinks for 15-20 people held in and around his office in the second week in December last year.
Another senior civil servant, Sue Gray, has since been appointed to lead the investigation, which now covers multiple - but not all - allegations of rule-breaking parties across Whitehall in the run-up to Christmas last year.
Additional reporting by PA
From news to politics, travel to sport, culture to climate - The Independent has a host of free newsletters to suit your interests. To find the stories you want to read, and more, in your inbox, click here.