The Speaker of the House of Commons has suggested Boris Johnson should "take responsibility" over an incorrect statement made to MPs at PMQs which many said was an example of the prime minister lying.
Sir Lindsay Hoyle first told a minister he "might be proved wrong" in response to a claim that Mr Johnson is "always right", before issuing a stinging statement to the Commons about correcting the record when errors are made.
The PM was accused of misleading Parliament after incorrectly saying the Labour Party voted against giving the NHS a 2.1% pay rise - in fact the Bill was nodded through the Commons and Labour did not contest it.
Referring to the PM's comments at Prime Minister's Questions on Wednesday, Sir Lindsay said: "All members should correct the record if they make an inaccurate statement to the House."
He was commenting after the prime minister's press secretary Allegra Stratton in a briefing with journalists refused 20 times to either admit a mistake had been made, apologise, or to correct the error.
Sir Lindsay said: "It is not dishonourable to make a mistake, but to seek to avoid admitting one is a different matter."
He cited the government's ministerial code, which he said "could not be clearer" about what is expected.
The code says: "It is of paramount importance that ministers give accurate and truthful information to Parliament, correcting any inadvertent error at the earliest opportunity."
When being quizzed by journalists on Wednesday, Ms Stratton said the Speaker had addressed the matter and corrected the record in the Commons immediately after PMQs, and so she considered the "matter to be closed".
But in an apparent slap down to the press secretary, Sir Lindsay told the Commons on Thursday morning that "the Speaker cannot be dragged into arguments about whether a statement is inaccurate or not. This is a matter of political debate".
Shadow Health Secretary Jon Ashworth accused Mr Johnson of misleading MPs and later used a social media post to claim the prime minister "lied at PMQs".
Sir Lindsay said members can correct the record "by raising a point of order or in debate or, in the case of ministers, they can make a statement or issue a written ministerial statement".
He added: "I said when I was elected Speaker that we needed to treat each other and the electorate with respect.
"What I have talked about today is an important part of that and I hope all members will act in that spirit."
Ms Stratton, on Thursday, explained why the PM would not correct the record by saying he was actually referring to the Queen's Speech which contained a Bill on the NHS budget, which Labour did vote against.
Earlier in transport questions, minister Mr Stephenson was asked by Labour's Grahame Morris (Easington) to correct the prime minister's previous denial over Transport for the North suffering a 40% budget cut.
Mr Stephenson replied: "The honourable gentleman has been in this House long enough to know that the prime minister is always right."
Mr Hoyle intervened and said: "You might be proved wrong."
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Mr Johnson claimed there had been "no such cut" to Transport for the North's budget when challenged about it last month during Prime Minister's Questions.
Board papers for the transport body, which aims to boost connectivity in the north of England, said core funding from the government would drop from £10 million in 2020/21 to £6 million in 2021/22.
Mr Johnson had been asked by Labour former minister Dame Diana Johnson how the cut fitted with his plan for "levelling up" the North.
In January, shadow transport secretary Jim McMahon also accused Mr Johnson of "misleading" MPs by claiming his 200-day-old comments on quarantine measures were recent.