Opposition leader Sir Keir Starmer led calls for a general election and a new UK government instead of allowing Boris Johnson to remain as prime minister until a new party leader is found.
Mr Johnson caved to intense pressure from his cabinet to step down on Thursday after the flood of resignations from his government approached 60.
In an address to the nation outside Number 10 Downing Street, Mr Johnson said: “I’ve agreed with Sir Graham Brady, the chairman of our backbench MPs, that the process of choosing that new leader should begin now and the timetable will be announced next week and I have today appointed a Cabinet to serve as I will until a new leader is in place.”
That process could take several months, allowing Mr Johnson to potentially remain in place until October.
Many politicians felt a caretaker prime minister would be a better option, with Mr Johnson's deputy Dominic Raab the most likely contender. He has stepped in for Mr Johnson twice before, when the prime minister was in hospital with Covid and when he underwent a nose operation. Crucially, he has also said he would not stand to be the next leader.
Sir Keir said Labour would use a House of Commons motion to attempt to oust him if the prime minister refused to hand over the reins to a caretaker prime minister. “He needs to go completely,” Sir Keir said. “None of this nonsense about clinging on for a few months.
“He's inflicted lies, fraud and chaos in the country. We're stuck with a government which isn't functioning in the middle of a cost-of-living crisis. And all of those that have been propping him up should be utterly ashamed of themselves.”
Sir Keir insisted Mr Johnson was "unfit to govern" and "cannot cling on for months". He tweeted: "If the Conservative party do not get rid of him, then Labour will act in the national interest and bring a vote of no confidence."
After reports surfaced that Mr Johnson's resignation was imminent, Sir Keir shared a letter on Twitter, welcoming the “good news”. But he insisted a change of Conservative leader would not be sufficient to address the problems blighting Britain and suggested the time had come for a general election to elect a new government — which he would lead.
“The Tory Party have inflicted chaos upon the country during the worst cost-of-living crisis in decades and they cannot now pretend they are the ones to sort it out,” Sir Keir wrote.
“They have been in power for 12 years. The damage they have done is profound. Twelve years of economy stagnation, 12 years of declining public services, 12 years of empty promises. Enough is enough.
“We don’t need to change the Tory at the top — we need a proper change of government. We need a fresh start for Britain.”
If a general election was called it is unlikely the Conservatives would win the same amount of support that they did in the last election in December 2019 when they won a landslide majority of 80 seats in parliament. With Mr Johnson at the helm of the party leading a campaign to “get Brexit done” the Tories won 43.6 per cent of the popular vote — the highest percentage for any party since 1979.
Public support for the ruling party has in recent months plummeted, as the government has weathered scandal after scandal and lost several by-elections to Labour and the Liberal Democrats.
Sir Ed Davey, leader of the Lib Dems, said it would be “ludicrous” for Mr Johnson to stay on until a new leader has been chosen by the Conservatives, and added his voice to growing calls for a change of government.
“Johnson may have gone but the stain on the Conservative Party can't be removed that easily,” he tweeted. “This cruel callous government must go.”
“The idea that the Conservatives might make Boris Johnson caretaker for anything is frankly ludicrous,” he added. “The man’s never taken care of anything in his life.”
Adrian Ramsay, co-leader of the Green Party, also in opposition, made clear his distaste for any plan that would see Mr Johnson remain in office as a caretaker prime minister over the coming months.
“How did the Conservative Party allow this to drag on for so long?,” he tweeted. “And are they really going to let him hang around for another three months? The work to heal our democracy needs to start well before then.”
News of Mr Johnson’s resignation broke on Thursday morning shortly after Iraqi-born MP Nadhim Zahawi, who was named as the new chancellor on Wednesday, publicly called on the prime minister to quit, saying the situation “is not sustainable and it will only get worse”. His withdrawal of support for the embattled leader came after Mr Johnson sacked cabinet minister Michael Gove on Wednesday evening after he too asked him to leave office. Mr Johnson on Thursday appointed Greg Clark to the position.
Ian Blackford, the Scottish National Party's leader in Westminster, used the prime minister's resignation to further push his party's campaign for Scottish Independence. SNP leader Nicola Sturgeon last month announced plans to hold a referendum on the matter in October 2023, after Scots voted to remain part of the UK in 2014. Mr Johnson on Wednesday ruled out handing Scotland's first minister the authority to hold another independence referendum.
“The only way for Scotland to escape the damage of Westminster control is to become an independent country, with the full powers needed to regain our place in Europe and build a fair and prosperous future,” Mr Blackford tweeted. “Whoever takes over from Boris Johnson must respect the democratic mandate the Scottish government has to hold an independence referendum — so we can escape Westminster control for good.”
Ms Sturgeon slammed Mr Johnson's appointment of a slew of new ministers in the wake of 59 resignations from his administration, saying the situation resembled a soap opera.
"How much more farcical is this going to get?" Ms Sturgeon wrote on Twitter. "If Johnson can’t even be trusted to resign properly, the Tories need to act to end it … now. People across the UK need and deserve better - especially now - than a badly written soap opera."
Sir John Major, a former Conservative prime minister, wrote to the chairman of the 1922 Committee to warn it was "unwise" for Mr Johnson to remain in office while his successor is chosen. Sir John suggested two options: either appoint Deputy Prime Minister Dominic Raab as acting prime minister or arrange for a new leader to be elected solely by an MPs' vote, without a ballot of party members.