European leaders are using Sir Keir Starmer’s struggles to increase Britain’s defence spending to convince him to join a €500 billion (£420 billion) rearmament scheme funded by common debt.

Poland, which holds the European Union’s rotating presidency, is pushing the project in response to Donald Trump’s criticism that European allies have piggybacked on US defence spending for too long.

Donald Tusk, Poland’s prime minister, this week argued that “we shouldn’t really care too much about what method we adopt to finance” a boost in defence spending on the Continent.

“There is no alternative to this: Europe must start defending itself and so it must start spending European money on this as well,” he added in a speech to the European Parliament in Strasbourg.