Downing Street security guards were forced to warn staff against holding social gatherings during lockdown, sources have revealed.
One No 10 insider claimed the officials - known as custodians - sent an email reminder round the building in the summer of 2020.
It followed a series of gatherings, including Boris Johnson ’s own birthday party in the Cabinet room for which he received a fine, that began as the country starting to emerge from its first lockdown.
Another source told the Mirror that the custodians were later forced to come round the building to speak to people directly, asking them to wind up events by 9pm.
It comes after an insider told BBC Panorama how one of the custodians was mocked when they tried to stop a party in full flow.
"I remember when a custodian tried to stop it all and he was just shaking his head in this party, being like, 'This shouldn't be happening'," they said.
"People made fun of him because he was so worked up that this party was happening and it shouldn't be happening.
"How did it happen then, when the rest of the country was living under strict lockdown?"
It comes ahead of the planned publication of Sue Gray’s report into lockdown parties today.
It is expected to be damning about the culture of partying that existed at the heart of government, while the rest of the country was following strict lockdown rules.
The report is expected to name Mr Johnson and give a damning verdict - along with pictures that could show he broke the rules.
It comes after bombshell claims that Boris Johnson suggested Sue Gray could just drop her Partygate report in a secretive meeting.
The Prime Minister - who is the Whitehall investigator's boss - met her this month after No10 officials said talks "may be something that she might want to consider."
No10 have refused to release any minutes. But it's now emerged Boris Johnson asked if there was "much point" in publishing her final verdict on lockdown parties after a police probe, the Times and Sky News reported.
The suggestion Boris Johnson tried to meddle with the inquiry piles fresh pressure after he was accused of lying to Parliament - due to photos of him raising a glass at a 13 November 2020 party he explicitly denied happened.
Cabinet ally Grant Shapps claimed the Prime Minister was "clearly not" partying at the leaving do for aide Lee Cain, telling Sky News: "He’d gone by to say thanks and raise a glass to a colleague who was leaving".
Mr Shapps also bizarrely said the PM "lost his mum during the period" - despite the fact Charlotte Johnson Wahl died 10 months after the photos were taken. Officials later insisted he was talking about the period of Covid generally, not the period of parties.
