However it is considered a breach of etiquette and Commons Speaker Sir Lindsay Hoyle, using standing orders, told him to withdraw from the House.
Here’s what you need to know about what he said, and what happened.
What did Ian Blackford say?
Mr Johnson had given a statement in parliament about the findings of the Sue Gray report. In her 12-page report on the partygate row, Ms Gray criticised “failures of leadership and judgment” by parts of No 10 and the Cabinet Office.
She said the Downing Street garden was “used for gatherings without clear authorisation or oversight” and “this was not appropriate”.
It was also revealed that police are investigating 12 events.
Mr Johnson told MPs in the House of Commons on Monday afternoon: “Firstly, I want to say sorry – and I’m sorry for the things we simply didn’t get right and also sorry for the way this matter has been handled.
“It’s no use saying this or that was within the rules and it’s no use saying people were working hard. This pandemic was hard for everyone.”
He added: “I get it, and I will fix it. I want to say to the people of this country I know what the issue is.”
Mr Johnson insisted he was “making changes” to Downing Street and the Cabinet Office, including by creating an Office of the Prime Minister with a permanent secretary to lead No 10.
Responding to the Prime Minister’s statement Mr Blackford had said: “We stand here today faced with the systematic decimation of public trust in government and the institution of the state, and at its heart a prime minister, a prime minister being investigated by the police.
“So here we have it. The long-awaited Sue Gray report, what a farce.
“It was carefully engineered to be a fact-finding exercise, with no conclusions. Now we find it’s a fact-finding exercise with no facts.
“So let’s talk facts. The Prime Minister has told the House that all guidance was completely followed, there was no party, Covid rules were followed and that ‘I believed it was a work event’.
“Nobody, nobody believed it then. And nobody, nobody believes you now, Prime Minister. That is the crux, no ifs, no buts, he has wilfully misled Parliament.”
Later in his speech he said: “Wait for the report we were told, here it is and it tells us very little, except it does say there were failures of leadership and judgement by different parts of No.10. It states that some events should not have been allowed to take place - that’s the Prime Minister’s responsibility. If there’s any honour, any honour in public life he would resign.”
How did the speaker of the house respond?
Mr Blackford was repeatedly asked by Speaker Sir Lindsay Hoyle to withdraw the claim Mr Johnson misled parliament, as it is considered against parliamentary etiquette to make such an assertion.
However, the SNP’s Westminster leader replied that the Prime Minister “may have inadvertently misled the House”, but Sir Lindsay asked: “To help me help the House, you’ve withdrawn your earlier comment and replaced it with inadvertently?”
Mr Blackford said: “It’s not my fault if the Prime Minister can’t be trusted to tell the truth.”
Amid shouting from the Tory benches, the Speaker said: “Under the power given to me by standing order number 43 I order the honourable member to withdraw immediately from the House.”
Mr Blackford walked out of the chamber before the Speaker had finished, with Sir Lindsay noting: “It’s all right, we don’t need to bother.”
What did Ian Blackford say afterwards?
Mr Blackford said Boris Johnson should have offered his resignation.
He told the PA news agency: “I think the public’s reaction is that here is a Prime Minister that set the rules that everybody else had to abide by.
“People couldn’t be with their loved ones when they were dying, couldn’t be with their loved ones in care homes, couldn’t hold proper funerals.
“And we have a Prime Minister that we now know has presided over the culture of parties in 10 Downing Street.
“Sixteen different parties on 12 dates, as revealed in the Sue Gray report, different dates having been referred for potential criminal activity to the Metropolitan Police.
“On the basis of that – there used to be honour and dignity in public life – based on that, the Prime Minister should have offered his resignation.”
Mr Blackford’s won praise from many people on twitter thanking him for his stance.
On Twitter, alongside a clip of when he was ordered out of the House Mr Blackford said: “This is what truth to power looks like at Westminster. A liar is allowed to keep his place- I am forced to leave for telling the truth. He misled the house, he must go. Tories must look themselves in the mirror and ask if they can allow this to go on much longer? Remove him now.”
He followed this with another tweet saying: “Thanks to all who have written to me following Parl today. Due to the volume of correspondence I can’t reply to everyone but all the views you have shared are valued. Truth and decency must always remain at heart of our politics. They are values that we must never give up on.”
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