The long-awaited defence investment plan boosts military spending by £15 billion, an increase of £1.5bn over the last two weeks, extra cash wrung out of the Treasury by new Defence Secretary Dan Jarvis.

And Mr Jarvis confirmed that the figure will rise further to 3 per cent of gross domestic product in the next parliament, and to 3.5 per cent by 2035.

The extra cash is to be splurged on drones above all, as well as fighter jets, nuclear arms and a larger weapons stockpile.

Investment in roads and energy projects are the immediate victims of the military increases, Sir Keir announced, amid rumours that his next stop after Downing Street may be as secretary-general of Nato.

Campaigners condemned the announcements, which were also designed to tie the hands of premier-presumptive Andy Burnham.

Stop the War Coalition vice-chair Chris Nineham said: “Never mind the cost-of-living crisis or the collapsing services he leaves behind, Starmer wants to be remembered as the man who ramped up spending on weapons to record levels.

“He claims he doesn’t want war, but that the best way to avoid it is to be prepared for it. This is a transparent lie.

“It is clear that security, defence and the fantasy and implausible threat from Russia, which is constantly talked up by ministers, generals and arms companies, are now the main ways that the ruling classes are justifying attacks on social programmes, on welfare and working-class living standards in favour of still more missiles.

“And that is why any effective campaign against public sector and welfare cuts needs to be making anti-war arguments.