Sir Keir Starmer has accused Boris Johnson of being a “complete bullshitter” who “took the piss” out of the public with his partygate explanations.
The Labour leader said the outgoing Prime Minister had been “found out” as the country has a sense that “this guy doesn’t mean a word that he says”.
He added that all the Tory leadership contenders are “B-grade candidates”.
Mr Johnson’s press secretary argued it was “hypocritical” of Sir Keir to call the PM a “bullshitter”, saying she “wouldn’t agree with that characterisation”.
Asked for his honest assessment of Mr Johnson’s legacy, Sir Keir told The Rest Is Politics podcast: “I think that he is a complete bullshitter and I think he’s been found out.
“And I’m really struck with the partygate stuff, because it wasn’t just that he did things which broke the rules, it’s that he then took the piss out of the public with his ridiculous defences afterwards.
“And in the local elections I accept that not everyone on doors was saying ‘it’s that that’s done it for me’, but there was a general realisation that this guy bullshits. And if he’s bullshitting about that, he’s probably bullshitting about everything.
“And all this stuff about levelling up, when people can see there’s not much happening round near them, I think there’s this sense that this guy doesn’t mean a word that he says, and that goes very, very deep, very deep.
“That’s why I don’t think there was ever any way back for him from that. And I think it’s really good for the country that we’re seeing the back of it.”
Sir Keir claimed that people like Mr Johnson “debase politics” and “drag everybody into the gutter”, which is “corrosive”.
He said: “I think one of the biggest issues and challenges in politics now is that because of people like Johnson who debase politics and drag everybody into the gutter, there is this general sense that you’re all the same.
“And that is the most corrosive thing, because once people think you’re all the same they lose heart in the idea that politics is a force for good, and that is a very dangerous place to get to.”
The Labour leader said the rule that MPs cannot accuse each other of being liars in the Commons chamber is “curious”.
“I know sometimes people say, ‘why don’t you just call him a liar, Keir?’ – but you can’t do it.
“Obviously there’s a frustration sometimes in not being able to do that, because if I’d been able to I’d have used it many, many times.”
Asked for a response to Sir Keir’s claims that Mr Johnson is a “complete bullshitter” who “took the piss” out of the public, the PM’s press secretary told reporters: “I would not respond with similar language of course.
“But I obviously wouldn’t agree with that characterisation. I think the Prime Minister has delivered a huge amount that was promised to the British public, not least getting Brexit done, which was delivering on the will of millions of people.
“And (it’s) possibly slightly hypocritical of the Leader of the Opposition to say such things when he voted against doing that 48 times”.
Labour denied that Sir Keir’s use of colourful language to describe the PM degraded the public debate.
Mr Johnson still faces a potentially damaging parliamentary investigation into whether he lied to MPs over the partygate row.
The Covid law-breaking events in Downing Street were among the scandals to force his resignation as Tory leader.
The Commons Privileges Committee’s inquiry threatens to further tarnish his legacy and could impact on his future as the MP for Uxbridge and South Ruislip.
Asked for his opinion on those running to be the next Tory leader, Sir Keir said: “I think they’re all B-grade candidates. I really don’t mind which of them I go up against.”