Military leaders who served under Labour have called on Sir Keir Starmer to increase defence spending to at least 3 per cent of GDP or risk emboldening Vladimir Putin.

Lord West, the former first sea lord, and Lord Dannatt, the former chief of the general staff, told The Telegraph that Sir Keir’s current target of 2.5 per cent was insufficient.

Both men linked Britain’s military spending with its ability to deter Russia, as Putin tries to tighten his grip on eastern Ukraine.

The interventions will pile pressure on the Prime Minister to go further and faster than he has indicated is probable in recent months.

Sir Keir has said he aims to raise defence spending from the current level of 2.3 per cent of GDP to 2.5 per cent, but he is yet to unveil a timeline for the plan. He scrapped Rishi Sunak’s target of doing so by 2030.

The timeline is expected to be revealed around June 2025, after the completion of Labour’s Strategic Defence Review, launched after their general election victory in July.

But Sir Keir’s decision to wait almost a year into office before announcing a timeframe for the increase has faced criticism, while the debate over the correct level of defence spending is also intensifying.