Pressure mounts on Met to justify no fine for PM over No 10 leaving drinks

The Metropolitan police are under mounting pressure to justify the decision not to fine the prime minister for attending a drinks gathering, as London’s mayor urged a public explanation.

The Met last week closed its investigation into Partygate, leaving Boris Johnson with one fine despite claims he was an active participant at several gathering that breached his own government’s Covid rules.

Related: No 10 officials say party attended by Johnson so cramped people sat on each other’s laps

On Monday that decision came under scrutiny when photos emerged of Johnson with a glass in his hand, surrounded by other people clutching glasses, apparently toasting departing Downing Street aide Lee Cain in front of a table littered with empty bottles of alcohol.

Sadiq Khan announced on Tuesday he had written to the acting Met commissioner, Sir Stephen House, asking that Britain’s biggest force explain to the public how decisions were reached.

Khan, as well as being mayor of London, oversees the Met as the police and crime commissioner for the capital. He said he was concerned that trust and confidence in the police was being lost as incredulity at the decision grows after the photos were leaked to ITV News.

A City Hall spokesperson said: “Sadiq has today written to the acting commissioner of the Met to seek a detailed explanation of the factors which were taken into account by investigating officers when decisions were made about whether to take action in individual cases in the Downing Street ‘Partygate’ investigation.

“He has asked them to take steps to also reassure Londoners by making this explanation to them directly, because he is concerned that the trust and confidence of Londoners in the police is being further eroded by this lack of clarity.

“The mayor has been clear he cannot and would not intervene in operational decisions, however with the investigation now complete, he has made this request in accordance with the Policing Protocol Order 2011 paragraph 23(g).”

Related: Three cheers for the blind eye of the police: where would our leader be without it? | Marina Hyde

The protocol says “The chief constable is responsible to the public and accountable to the PCC” and adds the chief is responsible for “notifying and briefing the PCC of any matter or investigation on which the PCC may need to provide public assurance either alone or in company with the chief constable”.

The same protocol also says the chief is responsible for “being the operational voice of policing in the force area and regularly explaining to the public the operational actions of officers and staff under their command”.

It also says the chief constable should remain “politically independent of their PCC”.

The Liberal Democrats have asked the police watchdog, the Independent Office for Police Conduct, to consider an investigation.