The former director general of the government's COVID taskforce has confessed to having a leaving party while under lockdown rules.
Kate Josephs posted a statement on Twitter saying she gathered in an office within the Cabinet Office to have drinks as a leaving do on December 17, 2020.
A total of 538 people died from COVID-19 on that day.
At the time, London was under Tier 3 restrictions, banning people from different households from mixing together indoors.
The news also comes amid a wider conversation of the culture within Downing Street, after Johnson issued a grovelling apology after he admitted attending a party in the gardens of Downing Street during the height of the first lockdown, when social gatherings were banned under COVID legislation.
Josephs tweeted: “As people know I previously worked in the Cabinet Office COVID Taskforce where I was Director General from July 2020 to December 18, 2020.
"I have been cooperating fully with the Cabinet Office investigations and I do not want to pre-empt the findings of the investigation.
"However as Chief Executive of Sheffield City Council I am responsible for leading the organisation and working with partners across the city and region to support our covid response and recovery.
"That is why I have decided to make a statement.
"On the evening of 17 December, I gathered with colleagues that were at work that day, with drinks, in our office in the Cabinet Office to mark my leaving the Civil Service.
"I am truly "sorry that I did this and for the anger that people will feel as a result.
"Sheffield has suffered greatly during this pandemic, and I apologise unreservedly.The specific facts of this event will be considered in the context of the Cabinet Office investigation.
"I did not attend any events at 10 Downing Street.
"I am grateful for the ongoing support of colleagues and partners and need now to ask that people allow the Cabinet Office to complete its investigation.
"I will not be able to respond to any further questions until the Cabinet Office investigation is complete.”
It was the day before a Christmas party was held in Downing Street, in which people brought “secret Santa” presents, and cheese and wine was laid out.
Boris Johnson's former press secretary Allegra Stratton resigned after she was caught on camera joking about the event on December 22.
The prime minister has been facing increasing calls to resign, including from within senior members of his own party, as public fury grows over repeated allegations of partying within Downing Street and the corridors of power, as the rest of the nation was banned from seeing loved ones.
Johnson is also facing plummeting ratings with voters, and a recent YouGov poll has put his favourability at an all time low - with 72% of the public saying they have an unfavourable opinion of the prime minister.
On Friday a spokesperson for the PM apologised to the Queen after it was revealed a party was held in Number 10 on the eve of the Duke of Edinburgh's funeral.
The Telegraph revealed on Thursday night that as Her Majesty prepared to say goodbye to her husband of 70 years, staff in Downing Street held a raucous leaving party that saw a staff member going to the shops with a suitcase to buy alcohol, and a swing used by the PM's toddler son was broken in the garden.
At the time England was under strict rules to stop the spread of COVID, and Prince Philip's funeral was limited to only 30 people.
More to follow...