The UK has supplied Ukraine with its Storm Shadow missiles, although ministers have not been drawn on details about their use, and £7.5 million funding for new attack and surveillance drones has also been announced.

At a press conference to close the G20 summit of the world’s largest economies in Brazil, the PM said: “There is irresponsible rhetoric coming from Russia and that’s not going to deter our support for Ukraine.”

There had already been “1,000 days of sacrifice”, Sir Keir said, but the UK would continue to ensure Ukraine has what it needs to fight the war “for as long as it needs”.

“On day 1,000 of Russia’s illegal war in Ukraine, I say again – end the war. Get out of Ukraine,” he said.

“In this moment when global challenges are affecting us at home, I take the view that British leadership matters.”

Sir Keir noted that Putin had been absent from the G20 for the third year running, adding he was “the author of his own exile”.

Asked about the summit’s joint communique regarding support for Ukraine – which Downing Street earlier described as “disappointing” – the PM stressed that the G20 group was united over Ukraine’s sovereignty.

He said: “The communique is absolutely clear on the UN charter and sovereignty and territorial integrity, and obviously that’s negotiated by quite a sort of diverse group.”