British Prime Minister Boris Johnson reacts as he speaks to the press during a visit of the Kent Oncology Centre at Maidstone Hospital, in Maidstone, on February 7, 2022, as part of a tour in Kent. AFP
Johnson -- facing calls to step down after months of scandals -- accused Starmer of failing in 2013 to take action against notorious celebrity paedophile Jimmy Savile as head of the country's prosecution service.
Labour leader Starmer, who led the Crown Prosecution Service (CPS) from 2008 to 2013, was not personally involved in the case but has previously apologised on behalf of the CPS for its failures.
Critics, including numerous Conservative MPs, have decried Johnson's claim -- made during a fractious parliamentary session -- noting it had been propagated by far-right conspiracy theorists.
Johnson later clarified the remark, noting Starmer's apology and apparent acceptance of responsibility, but refused to say sorry or retract his original statement.
It has come under fresh scrutiny after several dozen anti-lockdown demonstrators mobbed Starmer on Monday as he left parliament, with one protestor heard claiming he was "protecting paedophiles".
A video posted online showed the Labour leader being jostled before police, who arrested two people, intervened and escorted him to a car.
Within hours, several Tory lawmakers were renewing calls for Johnson to apologise.
"PM -- apologise please," Tobias Ellwood wrote on Twitter.
"We claim to be the Mother of all Parliaments. Let's stop this drift towards a Trumpian style of politics from becoming the norm. We are better than this."
Johnson himself took to Twitter to criticise Starmer's treatment Monday as "absolutely disgraceful".
"All forms of harassment of our elected representatives are completely unacceptable," he said, adding: "I thank the police for responding swiftly."
Dogged by 'Partygate
Meanwhile his ministers sought to distance the UK leader's previous attack on the Labour leader from the events.
"I don't think you can say that's why it happened," Technology minister Chris Philp told Sky News.
He noted other politicians and public figures had previously faced similar treatment from rowdy protesters.
But the incidents appear to have heightened unease within the restive Conservative Party at Johnson's conduct.
Ellwood is one of 13 Tory MPs to have publicly submitted a no-confidence letter in Johnson to a committee of backbench lawmakers with the power to call a leadership contest.
More are thought to have sent letters in without declaring them.
It follows weeks of damaging claims of parties in Downing Street during the pandemic, in a scandal dubbed "partygate".
The committee requires at least 15 percent, or 54, of the 360 Conservative MPs to write such letters to trigger a party leadership challenge.
Johnson has sought to move beyond the scandal by changing his top team, with several senior aides departing and a new chief of staff and director of communications hired.
However, his longtime chief policy advisor Munira Mirza unexpectedly quit last Thursday, specifically citing the Jimmy Saville claim in her resignation letter made public.
Meanwhile, Johnson is awaiting the outcome of a Metropolitan Police Service investigation into the numerous Downing Street gatherings and whether lockdown rules were breached.
The under fire British leader could face the humiliation of being fined by police -- an outcome likely to prompt a flurry of further no-confidence letters.
He is also heading into UK local elections in May with Labour enjoying a double-digit lead over his ruling Conservatives, on the back of the partygate scandal and a squeeze on living standards caused by surging inflation.
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