Mr Johnson has already lost one senior member of staff over the ongoing Christmas party scandal, and is facing calls to sack others – as well as to resign himself. But his former aide insists that the worst is yet to come.

The Government is under fire over reports of numerous parties held in Downing Street and elsewhere late last year, despite official Covid rules.

Video footage of the Prime Minister’s then-Press Secretary, Allegra Stratton, joking about a Christmas party in December 2020, just days after it is said to have taken place, emerged earlier this week.

This footage, featuring remarks Ms Stratton said she would regret “for the rest of my days”, led to her resignation.

If footage from after the event has produced such a significant backlash, Downing Street will be horrified by the prospect of footage emerging from the party itself.

That footage will emerge is, according to Mr Cummings, “inevitable”.

Writing on Twitter, he said: “There’s lots of pictures of the parties which will inevitably get out.

“And invite lists beyond Number 10, to other departments…”

Some, but not all of the parties which are believed to have taken place in November and December last year will now be subjected to an official investigation.

In a separate post on Thursday, Mr Cummings said “[our] focus should be [on the] actual party in the Prime Minister’s flat on November 13”.

The party – or “gathering”, as officials would prefer to put it – which has been at the centre of this week’s controversy took place on December 18.

The BBC has reported that Jack Doyle, Director of Communications at Downing Street, is believed to have been in attendance at the party.

He is accused of having given out a number of light-hearted awards amid party games, food and drink in an event that went on past midnight.

Laura Kuenssberg, the corporations Political Editor, said: “At the heart of Government there is no desire for other staff to quit or be forced out before [the investigation] has run its course…

“But other sources in Westminster are now questioning whether it is possible for Mr Doyle to stay in his job.”

In his most recent session of Prime Minister’s Questions – just hours before Ms Stratton announced her resignation – Mr Johnson told MPs he had been “repeatedly assured since these allegations emerged that there was no party and that no Covid rules were broken”.

The suggestion that his own communications director himself attended one of the Christmas parties raises a number of questions – not least about the quality of the assurances provided to him, or whether he was assured at all.

Source: Express.co.uk