UK opposition leader Keir Starmer on Sunday challenged Prime Minister Rishi Sunak to hold a snap general election, after three MPs, including Boris Johnson, quit parliament following a probe into alleged Covid-lockdown breaking parties in Westminster.
Nigel Adams and Nadine Dorries have also chosen to relinquish their posts as MPs.
Labour leader Mr Starmer said Mr Sunak "must finally find a backbone, call an election, and let the public have their say on 13 years of Tory failure".
He added: "This farce must stop. People have had enough of a shambolic Tory government and a weak prime minister no one voted for."
Mr Johnson on Friday announced he was standing down as a member of parliament, claiming he had been forced out by his political opponents.
He had been under investigation by a cross-party committee – chaired by Labour MP Harriet Harman and with a Tory majority – about whether he deliberately lied to parliament about parties in Downing Street when he was in office.
Speculation is rife about Mr Johnson's next move and whether he will attempt to run to become an MP again at the next general election, due next year.
Jacob Rees-Mogg, an influential backer of Mr Johnson, wrote in The Mail on Sunday that the former Tory leader could "easily get back into parliament at the next election".
He also warned Tory officials against blocking such a bid, saying it would "shatter our fragile party unity and plunge the Conservatives into civil war."
Mr Sunak was chancellor under Mr Johnson, and it was the former's resignation that ultimately triggered his then boss's demise.
Energy Secretary Grant Shapps, who served in Mr Johnson's cabinet, on Sunday said politics had "moved on" from the "drama" of the former prime minster's era.
He does not think Mr Johnson is in the right "mindset" to fight the next general election.
Mr Shapps told the BBC's Sunday with Laura Kuenssberg TV programme: "There is no kind of chance of him coming back and saying, 'Right, now I'm going to stand again'.
"From what I understand, even he has said he doesn't want to do that. So we are rather in the realms of the hypothetical."
Mr Shapps said Mr Johnson would have been "perfectly entitled to remain as an MP" but had instead "decided to step down".
He told Sky News's Sophy Ridge On Sunday programme: "I think people around the country inside and outside the party recognise that Boris was somebody with many qualities.
"But we are now in a world where there are different challenges to face and we've got new management in No 10 getting on with the job and getting on with the priorities of this country.
"I think the world has moved on from what was quite a dramatic period under Brexit and of course under the issues related to Covid, the vaccines and the rest of it."
He said the UK was in a "calmer period" under Prime Minister Rishi Sunak, who he said was "doing proper Conservative things" in a response to Mr Johnson accusing the government of ditching 2019 manifesto pledges.
Mr Shapps also said he disagreed with Mr Johnson's criticism of the Commons Privileges Committee's investigation into whether he misled MPs when he said Covid rules were followed in Downing Street during the pandemic.
But Mr Shapps said he has "no reason" to support the accusations, denying suggestions the investigation was motivated by a desire to reverse Brexit.
The former party chairman said while Mr Johnson had successes as prime minister, he thinks "people both in the Conservative Party and outside don't miss the drama" of his tenure.
