The comments from the leader of the opposition come amid reports the Prime Minister is set to oversee a mass clear out of Number 10 in an attempt to save his job.
The move, named ‘Operation Save Big Dog’, could see the likes of Mr Johnson’s principal private secretary, Martin Reynolds, who sent the now infamous ‘BYOB’ email invite, sacked.
Dan Rosenfield, the Prime Minister’s chief of staff, Stuart Glassborow, Reynold’s deputy, and some communications staff were also listed in the Sunday Times as being on borrowed time.
It also comes as the Liberal Democrats securing cross-party support for a no confidence motion in the Prime Minister.
On Sunday morning, the Labour leader repeated his calls for the Prime Minister to resign and labelled Mr Johnson a liar.
Sir Keir Starmer added that the Conservative politician had “lost authority” and “broke the law”.
He told the BBC’s Sunday Morning programme: “I think he (Prime Minister) broke the law. I think he’s as good as admitted that he broke the law. And, after all, Downing Street has now apologised to the Queen for some of the parties that have gone on.
“I know that the Government’s holding position is ‘let’s all wait for the Sue Gray report’.
“But I think it’s pretty obvious what’s happened, this industrial-scale partying had been going on at Downing Street, not much of it is really denied, and I think that the public have made up their mind. I think the facts speak for themselves. I think the Prime Minister broke the law, I think he then lied about what had happened.”
He added: “I’ve been prompted many, many times to call for the Prime Minister to resign.
“I always resisted but we reached a point, and this is the important thing, the Prime Minister has degraded the office of Prime Minister and he has lost all authority, not only in his own party, but in the country.
“Therefore, when he tries to persuade the public about how they should behave during the rest of the pandemic, he won’t be taken seriously and it’s not just the pandemic. At the moment, there are Russian troops in Ukraine, we have got energy bills, we’ve got the NHS, so he’s lost authority.”
The Labour leader added: “We’re now a country paralysed by the weakness of the Prime Minister. That’s why in the national interest he has to go.”
Speaking after submitting the no confidence motion in Mr Johnson, Liberal Democrat leader Ed Davey said that the Prime Minister posed a “threat to the health of the nation”.
The motion states that Parliament has no confidence in the Prime Minister as he has “broken the Covid lockdown laws his Government introduced, misled both Parliament and the public about it, and disastrously undermined public confidence in the midst of a pandemic”.
The motion has been signed by 18 MPs from four parties, including all 13 Lib Dems, two Labour MPs – Paula Barker and Mick Whitley – two from Plaid Cymru, and Stephen Garry from the Alliance Party.
Sir Ed said: “By remaining in Number 10, Boris Johnson is a threat to the health of the nation – no-one will take anything he says seriously and that is simply unacceptable during a pandemic.
“Conservative MPs should not only support our motion of no confidence but they should pressure Jacob Rees-Mogg to give the motion time for a vote and soon.
“The country deserves a chance to move on from this deceitful Prime Minister.”
However, during a chastening media round which included an emotional speech from Sky News’ Trevor Phillips who lost his daughter during the pandemic, Tory Party chairman, Oliver Dowden, claimed the Prime Minister was “contrite” over the allegations of rule-breaking.
Mr Dowden admitted there were “failings” in No 10, following a series of leaks about alleged lockdown parties, but he denied it was a resigning matter for Boris Johnson.
Instead the Government plans to “address the kind of culture that has allowed” the reported flouting of coronavirus laws to happen, in a hint of a shake-up at the top of Mr Johnson’s administration, he said.
It comes after The Sunday Times reported that the Prime Minister is devising a policy announcement blitz and a cull of his inner circle as he looks to survive the publication of senior civil servant Sue Gray’s report into so-called partygate.
Speaking to the BBC’s Sunday Morning programme, Mr Dowden said: “I can assure you the Prime Minister is both very contrite and deeply apologetic for what happened.
“But, more importantly, he is determined to make sure that this can’t be allowed to happen and that we address the underlying culture in Downing Street.
“There were failings: we should have done better, much, much better. We need to up our game, and that needs to be addressed, and I know the Prime Minister is committed to addressing that.”
It comes as a sixth Conservative MP called for Mr Johnson to quit, arguing that a change of senior officials would not reverse the “terminal damage” done to the Prime Minister by the allegations.
Former children’s minister Tim Loughton, in a post published on Facebook on Saturday, said: “It is not down to a simple Government policy change or a sacking of ministers or officials to put things right.
“In this case all roads lead back to Downing Street and the person whose name is on the front door.”