Shaun Bailey has stood down from an official role in the London assembly after it emerged he attended a “raucous” party amid the Covid lockdown in December last year.

The Conservative candidate for London mayor earlier this year stood aside as chair of the police and crime committee, a statement from the assembly’s Conservative group said.

It added: “He does not want an unauthorised social gathering involving some former members of the London mayoral campaign team last December to distract from the committee’s important work holding the mayor of London to account.”

The move places increased pressure on Boris Johnson and his Downing Street staff, who have been accused of holding a series of lockdown-defying social events in winter last year and earlier. Johnson has also faced claims he hosted events in his Downing Street flat.

The only central government figure to have resigned so far has been Allegra Stratton, the spokesperson for the Cop26 climate summit, who was previously Johnson’s press secretary. She stepped down after footage emerged of her and other No 10 staff joking about an apparent party on 18 December 2020 at Downing Street, one which officials had previously denied had taken place.

The revelations about Bailey’s party first emerged in the Times last Thursday, and there is speculation that more details of what took place at the event on 14 December 2020 could be published imminently.

According to the initial reports, staff danced and drank wine at the event, held in the basement of the Conservative campaign headquarters (CCHQ), the floor from where Bailey’s mayoral campaign was being run.

It took place on the day the then-health secretary, Matt Hancock, announced the capital was going into tier 3 restrictions. At the time, social mixing indoors with anyone from another household was already banned.

The event was attended by people from the campaign, as well as Tory staffers working on another floor. Bailey attended and was given a Lego set as a Christmas present.

The Times described the event as “raucous”, saying that a door was damaged during it. Conservative officials argue Bailey was there “briefly” to give a speech and thank his team, and that the unauthorised element took place later. CCHQ has disciplined four staff members.

Bailey has not commented since the reports emerged. However, the Labour group in the London assembly has said he must publicly account for what happened.

In a letter to Bailey, reported by the MyLondon website, Leonie Cooper, chair of the Labour group, said: “Londoners will have read the allegations that you attended a party at CCHQ, organised by your campaign, on 14 December whilst tier 2 restrictions were in place, and will understandably want answers.”

In the mayoral election in May, a vote delayed by a year due to Covid, Bailey ran the incumbent Labour mayor, Sadiq Khan, closer than expected, but lost by 55% to 45% once second-preference votes were counted.