However, the Prime Minister’s former chief of staff Dominic Cummings has suggested the situation may have arisen because Martin Reynolds, Boris Johnson’s principal private secretary (PPS), may have neglected to change the necessary settings. Mr Peston, ITV’s Political Editor, took to social media prior to Mr Johnson’s appearance at Prime Minister’s Question Time, tweeting: “Just to return to the party-invite email, ahead of the PM’s first PMQs since it was leaked to @PaulBrandITV, it is marked ‘OFFICIAL-SENSITIVE-No10 only’.
“Which means it is classified information. But it could only have been sensitive if the party broke the rules. Surely.”
However, replying to Mr Peston’s message, Mr Cummings cast doubt over the journalist’s interpretation.
He posted: “No10 private office emails do this by default.
“You have to deliberately change settings for it not to.
“If I emailed ‘I’ve lost my bobble hat again anybody seen it?’ it wd go as OFF-SEN by default.”
Mr Peston returned to the subject in the wake of Mr Johnson’s PMQs appearance, during which he apologised for attending the party, on May 20, 2020 for 25 minutes, but also claimed he believed the occasion to have been a work-related event.
All eyes are now on civil servant Sue Gray, who is currently undertaking an investigation into the various lockdown social events associated with Number 10 in 2020.
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Mr Johnson told MPs that he attended the event to “thank groups of staff” but “with hindsight I should have sent everyone back inside”.
He added: “I believed implicitly that this was a work event.
“With hindsight I should have sent everyone back inside.
“I should have found some other way to thank them.”
Mr Johnson said: “I should have recognised that even if it could be said technically to fall within the guidance, there are millions and millions of people who simply would not see it that way, people who have suffered terribly, people who were forbidden for meeting loved ones at all inside or outside, and to them and to this House I offer my heartfelt apologies.”
Mr Johnson’s press secretary later insisted that the PM was not a liar and “he is not resigning”.
Bookmakers Ladbrokes currently offer odds of 6/4 on Mr Johnson no longer being Prime Minister by the time of the May council elections.
And analysis of Google search data comparison site Casino Bee indicated online searches for ‘Who will replace Boris’ increased by 988 percent in the UK after Mr Johnson offered his apology.
Despite Mr Johnson’s statement, the controversy seems certain to rumble on.
Privately, Tory MPs have told Express.co.uk his apology had done little to draw a line under the affair.
Ms Gray’s conclusions are likely to be crucial in determining whether Mr Johnson is able to remain in his job.
Express.co.uk has contacted Number 10 for clarification about Mr Peston’s point.