Sir Keir Starmer's pledge to increase defence and security spending to 5 per cent of GDP by 2035 was last night branded 'a con'.

The Prime Minister will unveil the promise at a Nato summit today, with the alliance's 31 other members also expected to sign up to it.

It will commit Britain to spending 3.5 per cent of GDP on core defence spending, such as troops and weapons, plus a further 1.5 per cent on security-related domestic infrastructure.

The summit comes after Sir Keir's meeting yesterday with Ukrainian president Volodymyr Zelensky at No 10.

But critics pointed out that the pledge does not accelerate spending on core defence beyond what has already been promised by Labour.