Cabinet Secretary Simon Case, who has been tasked by Prime Minister Boris Johnson with investigating whether a series of alleged Christmas parties broke COVID restrictions in place in late 2020, shared drinks with a group of 15 to 20 staff at his office and in the waiting room outside at 70 Whitehall in mid-December 2020, two officials present told POLITICO and the Independent.

A third official, who did not attend, said the event was discussed the following week and they were asked whether they attended “waiting room drinks.”

In response to a series of questions about the officials’ accounts, the Cabinet Office said in a brief statement: “These allegations are categorically untrue.”

At the time, London was in Tier 2 restrictions, meaning people were not allowed to socialize indoors and were told to work from home where possible.

Several bottles of wine and Prosecco were poured in the office, the two officials present say, and in the waiting room of the cabinet secretary. Case carried a glass through the fray as he greeted staff who gathered for what one official characterized as “last-minute” drinks organized by WhatsApp, including civil servants from other departments.

Case was described as “in and out” of the gathering, drinking with colleagues. Crisps were also served and there were Christmas decorations on the tables, one of those present recalled. The same official said it was “a fairly regular occurrence” for civil servants to drink at their desks during this time but that the gathering in Case’s office was “a piss-up” including his team and members of other departments.

The Whitehall employees who spoke to POLITICO and the Independent questioned the suitability of Case and Darren Tierney, the director general of propriety and ethics, to lead the inquiry into Downing Street parties.

One said: “It would have been better for the civil service to bring in someone from the outside [to investigate] especially as other parties involved [special advisers] who are temporary civil servants.” Another said it was a “joke” that they were leading the inquiry.

Tierney is not alleged to have been at the drinks gathering but is said to have been aware that it took place.

Boris Johnson has faced sustained questions about staff Christmas parties since the Mirror reported that officials drank wine and exchanged gifts via a Secret Santa on December 18, 2020. The prime minister announced last week he was putting Case in charge of an inquiry into the claims, a probe that has since expanded to include other gatherings alleged to have taken place on November 27 and December 10.

Johnson has also apologized “unreservedly” for video footage published by ITV News that shows members of the prime minister’s staff joking about the alleged celebration. Allegra Stratton, Johnson’s former spokeswoman, resigned over the video, saying she would “regret those words for the rest of my days.”

The prime minister said last week he had asked the cabinet secretary to “establish all the facts and to report back as soon as possible.” Findings had been widely expected this week. Johnson pledged: “It goes without saying that if those rules were broken, there will be disciplinary action for all those involved.”

Johnson is experiencing one of his toughest weeks since becoming prime minister, and overnight saw his party lose a by-election in a seat that the Tories had held for almost 200 years. Earlier this week, Johnson suffered his biggest rebellion in the House of Commons to date over new COVID restrictions, with many insiders saying his credibility has been seriously dented.

Stories about Christmas parties keep coming, with the Mirror on Tuesday publishing fresh details of a Zoom quiz hosted by the prime minister, as well as an image of a separate party held in Conservative Campaign Headquarters by former London mayoral candidate Shaun Bailey. The Independent reported Thursday that the prime minister joined officials for drinks in Downing Street during the first coronavirus lockdown in May 2020.

Case was made the U.K.’s top civil servant in September 2020 — the youngest person ever recruited to the role — after he helped shape the U.K.’s response to the coronavirus pandemic.

He was previously director general at the now-defunct Department for Exiting the EU, where he worked on Irish border negotiations under Theresa May, and has served as private secretary to the Duke of Cambridge, as well as advising David Cameron and directing strategy at intelligence agency GCHQ.