Susan Acland-Hood, permanent secretary at the Department for Education (DfE), admitted that she attended the gathering, where there were drinks and food, on December 10 last year in the department’s canteen.

She told MPs that if any DfE staff, including herself, were found to have broken the rules then they would face disciplinary action.

Her comments came after the DfE admitted it held a social gathering of staff ahead of Christmas in contravention to coronavirus social-distancing rules.

The party is said to have been arranged by Gavin Williamson when he was Education Secretary

The Mirror reported that Mr Williamson threw a party and delivered a short speech at the event, which took place while London was in Tier 2, which banned any social mixing between households.

When asked about the reports during a Public Accounts Committee hearing, Ms Acland-Hood said the gathering for staff was attended by around “two dozen” people – including herself and Mr Williamson.

She added that the event would form part of the Cabinet Secretary’s investigation into a gathering in Number 10 during the same month.

Ms Acland-Hood said: “While this was a work-related gathering, looking back we accept that it would have been better not to have gathered in this way at that particular time.”

She confirmed to MPs that the gathering at the DfE office was instigated by then education secretary Mr Williamson as he wanted to “thank staff” for their work during the pandemic.

Her comments came as Boris Johnson ordered an investigation into claims Downing Street staff broke lockdown rules by holding a Christmas party on December 18 last year – when London was in Tier 3.

Ms Acland-Hood told MPs: “I have spoken to the Cabinet Secretary and the gathering that was held will be part of his consideration as part of the investigation that was announced in PMQs.”

Addressing the committee, she said “drinks and snacks” were brought to the gathering at the office by attendees, but “no outside guests” were present.

When asked if it was an organised event, Ms Acland-Hood added: “It was to some extent in the sense that the Secretary of State had said he wanted to thank staff together for the work that they had done.”

Allegra Stratton resigns over Christmas party comments

Gavin Williamson's 2020 Christmas party for staff also placed under investigation