Angela Rayner has today branded Boris Johnson "a coward" and said his actions during Partygate are unforgivable.
The Deputy Labour Leader said the former Prime Minister "never accepted responsibility" for his actions - and it has now "caught up with him".
Her comments came a day after Johnson announced he will quit as an MP with immediate effect in a bombshell statement accusing his enemies of trying to "drive him out".
In a bullish and lengthy statement, Johnson claimed the Privileges Committee had "not produced a shred of evidence that I knowingly or recklessly misled the Commons".
And he claimed the committee was "determined to use the proceedings against me to drive me out of Parliament".
Speaking on BBC Breakfast this morning, Ms Rayner said that "rather than face the music", Mr Johnson "decided to jump".
She said: "I think he's a coward, he knew that the Privileges Committee, which has a Conservative majority on it, had got the evidence that he knew all along and he's just never accepted responsibility for his actions.
"I think it's just how Boris Johnson has been throughout his life but it's caught up with him now. And rather than face the music, he's decided to jump."
She added: "He's tried to blame everybody else when actually, he's got to accept responsibility for the consequences of his own actions."
Ms Rayner also said that Mr Johnson let down voters who handed him his landslide election victory in 2019, arguing that the former PM has shown he had "no respect for the British public".
She told BBC Radio 4's Today programme: "I think the people put their trust in him because they thought he was about change and he was about putting them at the heart of decision-making, and he has let them down truly in the most devastating way at the time when they needed him most.
"No one could have predicted what happened to this country during the pandemic, but at the time when the public needed him the most, he basically was partying and lying to them at a time when they couldn't see their loved ones.
"And that is unforgivable.
"The fact that he cannot recognise the damage that he has done, and he has tried to stuff the Lords with people that propped him up and helped him and assisted him at the time shows us that actually he had no respect for the British public.
"It was all about Boris and it has always been all about Boris to him, and people will be left disappointed by his legacy."
In his statement, Mr Johnson said: "'It is very sad to be leaving Parliament - at least for now - but above all I am bewildered and appalled that I can be forced out, anti-democratically, by a committee chaired and managed, by Harriet Harman, with such egregious bias."
The ex-PM was handed the committee's report earlier this week and was given two weeks to respond.
But last night, he ranted: "Their purpose from the beginning has been to find me guilty, regardless of the facts. This is the very definition of a kangaroo court."
The Privileges Committee has been examining whether Mr Johnson misled Parliament when he dismissed the Mirror's reporting on Partygate.
