LONDON (AP) — U.K. Prime Minister Boris Johnson’s first choice to investigate allegations that government officials held Christmas parties last year when COVID-19 rules barred such gatherings has stepped aside after he, too, was caught up in the “partygate” scandal.

Simon Case, the head of the civil service, resigned from leading the investigation after the Guido Fawkes website reported Friday that Case’s department held two parties in December 2020. Johnson tapped Sue Gray, a former senior government ethics adviser, to take over the inquiry.

The moves came after Johnson’s Conservative Party suffered a stunning defeat in a parliamentary by-election that was attributed in part to “partygate," which has dominated British news headlines for two weeks. The idea that politicians and civil servants in London were partying when lockdown rules separated citizens from loved ones angered the public.

Angela Rayner, deputy leader of the opposition Labour Party, said Gray now has the task of restoring public trust. One point in Gray’s favor may be that she was based in Belfast a year ago as the senior civil servant in the Northern Ireland Department of Finance.

“At the moment, people are saying, ‘Which department didn’t have a party?‘” Rayner said. “It’s incredibly disappointing because we all know what was happening when these parties were going on: people couldn’t see their loved ones who were dying and were making incredible sacrifices.’’

Case was brought in to investigate the scandal after a video surfaced of a mock press conference where some of Johnson’s staff appeared to make light of a party that violated the rules. Until that time, the prime minister had steadfastly denied that government officials had broken any lockdown rules.

The Times of London newspaper reported Saturday that one of the events held by Case’s department, the Cabinet Office, was listed in digital calendars as “Christmas party!” and was organized by a member of Case’s team.

The Cabinet Office said Friday that the event was a virtual quiz in which a small number of people who had been working together in the same office took part from their desks.

“The Cabinet Secretary played no part in the event but walked through the team’s office on the way to his own office,’’ the office said in a statement. “No outside guests or other staff were invited or present. This lasted for an hour and drinks and snacks were bought by those attending. He also spoke briefly to staff in the office before leaving.”