Rishi Sunak signalled his reluctance to commit to a significant increase in UK defence spending on Monday despite heightened tensions with Russia, even as the prime minister signed off on a ￡4.2bn contract for five more warships for the Royal Navy.

Speaking en route to Indonesia for the G20 summit, Sunak defended the UK’s commitment to security and its allies. But he avoided answering whether he would match the promise of his predecessor Liz Truss to lift defence spending to 3 per cent of gross domestic product by 2030, well above Nato’s 2 per cent target.

“You talk about my predecessor’s target. My other predecessor [Boris Johnson] before that’s target was an aspiration to get to 2.5 per cent?.?.?.?and then the Nato target itself is 2 per cent,” he said.