Sir Keir Starmer has pledged to increase defence spending to 2.5 per cent of GDP "as soon as resources allow", as well announcing a new nuclear deterrent "triple lock".
The Labour leader also proised to conduct a strategic review of defence and security to be "clear what the priorities are".
The latest pledge brings Labour in line with the Government, with Jeremy Hunt having said he wants defence spending to increase to 2.5 per cent.
According to estimates from Nato, the UK's spending on defence stood at 2.1 per cent of GDP in 2023.
Sir Keir Starmer has pledged to increase defence spending to 2.5 per cent of GDP "as soon as resources allow", as well announcing a new nuclear deterrent "triple lock"
PA
On a visit to Barrow today, the Labour Leader said the UK’s nuclear deterrent is the “bedrock” of Labour’s plan to keep Britain safe. He announced a new "triple lock" commitment to the UK nuclear submarine programme.
Starmer will commit to building four new nuclear submarines at Barrow, to maintaining Britain’s continuous at-sea deterrence, and to all future upgrades needed.
Speaking later, Starmer is expected to say: "In the face of rising global threats and growing Russian aggression, Labour’s commitment to our UK nuclear deterrent is total".
Starmer said nuclear weapons are "expensive" but "absolutely vital and needed".
Annual running costs are estimated at around 6 per cent of the defence budget, amounting to £3 billion for 2023-24.
Asked about defence spending, Starmer told the i: "Obviously we want to get to 2.5 per cent as soon as resources allow that to happen.
"That was the position when Labour left government and we absolutely stand by our commitment to Nato."
Defence Secretary Grant Shapps said Labour can't "be trusted" with defence, claiming that the Labour leader and shadow defence secretary "tried twice to put Jeremy Corbyn in charge of the nation's armed forces".
He added: "The same man who wanted to scrap our nuclear deterrent, dismantle Nato and questioned the integrity of British intelligence community."
"They are not the party to be trusted with our nation's defences."
The SNP also hit out at Westminster's plans for defence, saying both Starmer and Sunak are "focused on the wrong priorities".
SNP defence spokesperson Martin Docherty-Hughes MP: “Westminster has already wasted billions of pounds of taxpayers’ money on nuclear weapons and expensive nuclear energy.
“It is therefore grotesque that Sir Keir Starmer is prepared to throw billions more down the drain when his party claim there is no money to improve our NHS, help families with the cost of living or to properly invest in our green energy future.
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Defence Secretary Grant Shapps said Labour can't "be trusted" with defence
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“This money would be better spent on a raft of other things – not least investing in the green energy gold rush, which would ensure Scotland, with all its renewable energy potential, could be a green energy powerhouse of the 21st century.
“And while the UK Government wastes millions misfiring Trident missiles at the Defence Secretary, the urgent priority is more money for conventional defence and for our armed forces, who are underpaid and under-resourced.
“With both Rishi Sunak and Keir Starmer focused on the wrong priorities, it is only the SNP standing up for Scotland’s interests and Scotland’s values.”