In the heated row, the Tory leader savaged Sir Keir's response to Iran, accusing him of being "weak" for focusing on benefits spending rather than investing more in defence. She said that the PM was putting "his job security over our national security", as Sir Keir hit back by saying Mrs Badenoch was showing her "irrelevance".
After the Speaker of the House of Commons intervened during their bitter exchange, Sir Keir stood up to speak before Mrs Badenoch had finished her question, with Sir Lindsay Hoyle telling the Prime Minister to sit down so the Tory leader could continue.
The Commons descended into chaos after the row, with MPs shouting and jeering.
Sir Keir and Mrs Badenoch came to blows after she called for the UK to take more direct action in supporting the US's bid for regime change in Iran.
Sir Keir has come under fire from US president Donald Trump over his response for reportedly not letting the Americans make use of the Diego Garcia airbase in the Chagos Islands to attack Iran.
Mr Trump said he was "not happy with the UK" and, in a wounding rebuke, said of the PM: "This is not Winston Churchill we're dealing with."
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Mr Trump also said that he was "very surprised" by the British Government's inaction. He added: "And it's taken three, four days for us to work out where we can land, it would have been much more convenient landing there as opposed to flying many extra hours."
Sir Keir has said that HMS Dragon, a warship, will be sent to the region to protect British bases there, but it has still not left the UK.
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Trump says this is no Winston Churchill he deals with (Image: Getty)
The shocking attack by the president came as war engulfed the region after the US attacked Iran on Saturday and killed the country's Supreme Leader, Ayatollah Ali Khamenei.
Attacks have continued over recent days, with Tehran retaliating across the Gulf states and beyond.
The president has been critical of British responses to the war, and has previously said the Prime Minister was "unhelpful" when the UK chose not to be involved in the initial attack."
Speaking to The Sun over the weekend, he said the PM "has not been helpful", adding: "I never thought I’d see that. I never thought I’d see that from the UK. We love the UK. It’s a different world, actually. It’s just a much different kind of relationship that we’ve had with your country before."