Sir Keir Starmer said Labour would stick to its commitment not to raise taxes to reach a new defence and security spending pledge of 5% of GDP by 2035.
The Prime Minister is meeting leaders of other Nato member countries in The Hague, where they are expected to formally agree the target, made up of 3.5% on “core defence” and another 1.5% on “resilience and security”.
He rejected that tax rises would be needed to pay for higher defence spending.
“Every time we’ve set out our defence spending commitments, so when we went to 2.5% in 2027/28, we set out precisely how we would pay for it, that didn’t involve tax rises.
“Clearly we’ve got commitments in our manifesto about not making tax rises on working people and we will stick to our manifesto commitments,” the Prime Minister told reporters in the Netherlands.
He said the current commitment to get defence spending up to 2.5% of GDP by 2027/8 was not coming at the expense of welfare, but rather from cuts to overseas development aid.
“So, it’s a misdescription to suggest that the defence spending commitment we’ve made is at the expense of money on welfare.”
Donald Trump is among the world leaders at the summit, and told reporters on the way to the Netherlands that it would depend “on your definition” when asked if he would commit to Nato’s Article 5, which requires members to defend each other from attack.
At a Cabinet meeting on Tuesday morning, Sir Keir underscored that national security is the “first duty” of Government.
His trip comes as the Government publishes its national security strategy, setting out plans to make the UK “more resilient to future threats”.
Downing Street has described the 5% goal as “a projected target” that allies will review in 2029 when Nato carries out its next capability assessment.
It is a significant jump from the current 2% Nato target, and from the UK Government’s aim of spending 2.5% of gross domestic product (GDP) on defence from 2027 and 3% at some point after the next election.
But the figure is in line with the demands of US President Donald Trump, who has called for Nato allies to shoulder more of the burden of European defence.
The Government expects to spend 1.5% of GDP on resilience and security by 2027.
The details of what counts towards that target are due to be set out during this week’s summit, but it is likely to include spending on energy and border security as well as intelligence agencies.
But increasing core defence spending to 3.5% will not happen until 2035, with at least two elections likely to take place before then.
The Institute for Fiscal Studies estimates that an increase in core defence spending from 2.6% to 3.5% would cost around £30 billion more a year.
It noted however that the plans concern spending far in the future – due in 10 years’ time – and therefore may not affect the Government’s spending review or autumn budget decisions, but prompt the chancellor to revise plans at the 2027 spending review.
Spending 3.5% of national income on defence is “certainly not unprecedented” but much more is now spent on health than in the past, IFS researcher Bee Boileau noted.
Shadow foreign secretary Dame Priti Patel said the Government had not been clear enough about how it would reach the core defence spending goal, claiming ministers had only offered “smoke and mirrors”.
She added: “So, when will he actually deliver a plan to get to 2%, and why won’t he heed our calls to hit 3% by the end of this Parliament, which would be vital, and a vital stepping stone on the way to that higher defence spending that he is seeking.”
The Nato gathering comes amid the backdrop of escalating Middle East tensions and the ongoing war in Ukraine.
Sir Keir has urged Israel and Iran to get back to the fragile ceasefire brokered by Donald Trump.
Ukrainian President Volodymyr Zelensky is expected to attend the summit, but not take part in the main discussions of the North Atlantic Council.
Nato secretary-general Mark Rutte described the move to spend more on defence as a “quantum leap” that would make the organisation “a stronger, a fairer and a more lethal alliance”.
But it was reported on Sunday that Spain had reached a deal that would see it exempted from the 5% target.
Prime Minister Pedro Sanchez said that Spain would be able to keep its commitments to the 32-nation military alliance by spending 2.1% of GDP on defence needs.
