Last week, the UK’s most senior police officer announced that the Met would be launching a criminal investigation into alleged breaches of Covid-19 rules at parties involving Downing Street and Whitehall over the past two years.

But Scotland Yard was accused of “censoring” civil servant Sue Gray’s report into the Downing Street parties after ordering that it be removed of any references to the most serious rule breaches which would be the focus of its own investigation.

Speaking to the Local Democracy Reporting Service on Monday, Mayor of London Sadiq Khan said that the Met should be able to conduct its investigation “without political interference” but said he hoped it would be “transparent” and “expeditious”.

Read more: Police launch Downing Street Covid breach investigation

Mr Khan said: “I think all of us are frustrated by the delays from the civil servant and from the police. I think it’s important, though, that we allow them to do their job. How would we feel if the police were to turn around and say they can’t have a proper investigation, justice can’t occur, because it’s been prejudiced by the full publication of the report?”

The Met’s handling of the Downing Street parties scandal has added to the growing pressure on the force and its leader Cressida Dick following a series of damaging scandals and PR disasters over the past 12 months.

Last year, just months after being personally named in the Daniel Morgan report which accused the Met of “institutional corruption”, Cressida Dick had her tenure as Met Commissioner extended by two years by Home Secretary Priti Patel, a decision supported by the Mayor of London.

On Monday, Sadiq Khan said that he stood by his decision to support Cressida Dick’s reappointment.

Read more: Sadiq Khan calls for investigation into Met’s handling of Sarah Everard vigil

Mr Khan said: “I think the Home Secretary was right to reappoint Cressida Dick for two years. I supported that reappointment from the Home Secretary, but one of my jobs is to hold her to account. One of the jobs of the home affairs select committee, the London Assembly police and crime committee, the Home Secretary, myself, and Parliament – is to hold the police to account, as indeed it is the job of the IOPC and Her Majesty’s Inspectorate.”

But he added that “the Met have a tough job to do” and that “they need our support”.

He said: “We police by consent. My job as Mayor is to be an advocate, a champion for the Met at the same time as holding them to account. It’s really important that I do both.”