A day after the report was published, describing a boozy culture in Downing Street during COVID-19 lockdowns, Conservative lawmakers John Baron and David Simmonds said they could no longer support the prime minister.
Their voices on Thursday add to a growing list of Conservative lawmakers who have called for Johnson to resign over what has been dubbed "Partygate", despite the prime minister's repeated apologies.
Baron, first elected in 2001, said he was withdrawing his support because he believed Johnson had "knowingly" misled parliament -- a charge the prime minister denies but which is being investigated by a parliamentary committee.
"Given the scale of rule-breaking in No. 10, I cannot accept that the prime minister was unaware. Therefore his repeated assurances in parliament that there was no rule-breaking is simply not credible," he said in a statement.
"Having always said I would consider all the available evidence before deciding, I'm afraid the prime minister no longer enjoys my support - I can no longer give him the benefit of the doubt."
Simmonds, who was elected in 2019, said Johnson had lost the confidence of the public.
"Accordingly it is time for him to step down so that new leadership can take forward the important work of the government," he said in a statement.
More than 15 Conservative lawmakers have publicly called for Johnson to quit since the reports of lockdown-breaking parties began to steadily drip into the media. But Johnson has refused, saying he still has work to do in government.
To trigger a confidence vote in Johnson's leadership, 54 Conservative lawmakers in parliament must write letters calling for one to the chairman of the party's 1922 Committee.
The letters are confidential, so the chairman is the only person who knows how many have actually been submitted.
