Mr Javid’s position suggests a hardening of government messaging on the issue, with ministers now avoiding answering questions about whether Mr Johnson should resign.

On Sunday Oliver Dowden, the Conservative chairman, said the Prime Minister would not leave office, but by Tuesday Dominic Raab had told journalists that lying to Parliament was “normally” a resigning matter.

The question of whether Mr Johnson lied to the Commons about knowing about the parties in Downing Street is one his critics hope will be resolved by Ms Gray’s inquiry.

Steve Baker, a prominent Tory backbencher, told the BBC’s Political Thinking podcast that Mr Johnson “must go” if it is found he broke the law or lied to Parliament, but said “we are all waiting” for the Gray inquiry’s findings.

“We didn’t make Boris Johnson prime minister for his meticulous grasp of tedious rules, but this is appalling and the public are rightly furious,” he said. “At the moment I’m afraid it does look like checkmate – but whether he can save himself, we’ll see.”

Mr Javid also said David Davis’s call for Mr Johnson to resign had been “damaging” to the Prime Minister.

Mr Davis urged Mr Johnson to stand aside on Wednesday, telling him: “In the name of God, go.”. He told The Telegraph’s Chopper’s Politics podcast that he thought the chance of Mr Johnosn being in Downing Street by Christmas stood at 30 per cent.