LONDON — Boris Johnson is under renewed pressure after Downing Street admitted staff gathered inside No 10 during the first Covid lockdown to mark his birthday.

ITV News reported that up to 30 people attended the June 2020 event, sang Happy Birthday and were served cake.

No 10 said staff had "gathered briefly" to "wish the prime minister a happy birthday", adding that he had been there "for less than 10 minutes".

But a number of MPs have expressed criticism over this latest revelation.

Rules at the time - 19 June 2020 - banned most indoor gatherings involving more than two people.

ITV News said the birthday event had taken place in the Cabinet Room just after 14:00 BST that day, adding that it had been arranged as a surprise for Mr Johnson by his then fiancee, Carrie Symonds, after he returned from an official trip to a school in Hertfordshire.

A Downing Street spokeswoman said that a group of staff working in No 10 "gathered briefly in the Cabinet Room after a meeting to wish the prime minister a happy birthday".

The spokeswoman added that Mr Johnson "was there for less than ten minutes".

Environment Secretary George Eustice denied ITV's claim that 30 people had gathered in the Cabinet Room, saying the number of staff present was "closer to 10" and it "was literally just a birthday cake brought in at the end of the day".

The BBC has learned that Sue Gray, the senior civil servant compiling a report into gatherings on government premises during Covid restrictions, already knew about the 19 June event.

Her findings are expected to be published later this week.

But in the meantime, a number of MPs have denounced the latest revelation.

Shadow Northern Ireland secretary, Labour MP Peter Kyle, told BBC Two's Newsnight that "there is no ambiguity" regarding the allegations of parties at No 10 during lockdown.

He added that Ms Gray has a "pretty straightforward job now".

Former Conservative Party chair Baroness Warsi told the BBC News Channel it was time for Mr Johnson to "think long and hard about what is in the best interest of this country".

"The question he should be asking himself every morning is, 'Is me staying in office allowing me to run this office in a way in which is making the country better, or am I a distraction?'" she added.

Conservative MP Andrew Bridgen told the BBC's Newsnight programme that the revelations of a gathering at No 10 to celebrate the prime minister's birthday during the first coronavirus lockdown, "could well be the straw that breaks the camel's back".

In a tweet, the former Scottish Conservative leader Ruth Davison revealed that her partner also has a birthday on 19 June but added: "We marked it in 2020 by inviting one other household to sit outside, socially distanced, in our garden."

And Labour leader Sir Keir Starmer repeated his call for Boris Johnson to stand down, saying: "The prime minister is a national distraction and he's got to go".

But the PM did receive some support from Cabinet colleagues.

Culture Secretary Nadine Dorries said in a tweet: "So, when people in an office buy a cake in the middle of the afternoon for someone else they are working in the office with and stop for 10 minutes to sing happy birthday and then go back to their desks, this is now called a party?"

The fact that Mr Johnson had been publicly presented with a birthday cake during the school visit a few hours earlier provides all of Wednesday's newspapers with a picture of the prime minister for many of them to use on their front pages.

Some Tory MPs, including the party's Scottish leader Douglas Ross, have also called on Mr Johnson to go, but many more say they are waiting for Ms Gray's findings before making a judgement.

At total of 54 MPs must write to Sir Graham Brady, chairman of the backbench 1922 Committee, declaring no confidence in the PM, to trigger a leadership contest.

Jo Goodman, co-founder of the Covid-19 Bereaved Families for Justice group, said the Downing Street birthday gathering "was the day before what would have been my dad's 73rd birthday, shortly after he had passed away from Covid-19.

"It was a horrible time for my family, but we stuck to the rules, not even being able to hug to comfort each other."

She added it was "completely sickening" that No 10 staff had gathered indoors to eat cake for the PM's birthday, saying: "While dozens sang Happy Birthday to him, families couldn't even sing in memory at their loved ones' funerals." — BBC