Sir Keir Starmer said the UK had to be prepared for war to be able to deter potential enemies as he set out the £15 billion defence investment plan (Dip).
The Prime Minister acknowledged some other areas of Government spending would be slashed in order to fund defence, with road and energy projects scrapped to pay for the military.
Sir Keir said: “When the world is arming and aggression is rising, the best way to avoid war is to prepare for it.
“The best way to defend is to deter, to have the strength to make your adversaries think again before they act.
“And that is what we are doing.”
Annual defence spending will increase from £54 billion when Labour came to power to £80 billion by 2029, Sir Keir said.
The plan reverses the “corrosive hollowing out” of the armed forces, he said in a speech at a drone company in Berkshire.
Chancellor Rachel Reeves, who was also at the event, said the extra money for the Dip had come from “reprioritising spending” across Government.
Sir Keir set out where the trade-offs had been made, with the money found by raiding Whitehall capital budgets, as he acknowledged there were “no easy answers”.
He said if the Government had chosen to “slash funding to our public services in favour of defence”, then “we would be fundamentally weaker as a nation, more fractured as a society, less able to defend ourselves when our enemies prey on social division”.
The Dip would not take resources away from day-to-day spending on frontline services such as health and education, he said.
“Instead, it is funded by reallocating spending from across Government departments, reallocating capital budgets by one penny in every pound, while still maintaining public investment at the highest sustained levels since the 1970s.”
He added: “Therefore, some capital projects, for example on roads and energy, which are important but not immediately vital, will no longer go ahead as planned.”
The Dip, which was originally due to be published last year following the strategic defence review, was repeatedly delayed by Whitehall wrangling over the funding.
John Healey quit as defence secretary earlier this month, claiming he had only been offered £13.5 billion for the Dip.
His successor Dan Jarvis appears to have wrung some extra money out of the Treasury and his Cabinet colleagues in order to reach the £15 billion figure, although defence experts still believe this is not enough.
The announcement of the Dip could be one of the final acts of Sir Keir’s premiership as he attempts to secure his legacy before handing over power, which could happen within weeks if – as expected – Andy Burnham is the only candidate to replace him.
Sir Keir said he is “absolutely certain” his successor as prime minister will build upon the Government’s increases in defence spending.
The UK has committed to the Nato target of spending 3.5% of gross domestic product – a measure of the size of the economy – on defence by 2035.
The Dip will take spending to 2.7% in 2027-28, which officials claimed puts the Government on target to meet the Nato goal.
It means that across the next four years there will be £298 billion of defence investment, including the extra £15 billion announced on Tuesday.
But this falls short of the £28 billion military chiefs had reportedly requested, and scepticism remains on whether the Dip will be enough to protect the country.
Measures in the Dip include:
– Some £64 billion for the renewal of the UK’s nuclear deterrent, including new submarines, a sovereign warhead and F-35A fighters capable of carrying nuclear bombs.
– More than £8 billion for the global combat air programme (Gcap) with Japan and Italy to build the next generation of jets for the RAF.
– Around £5 billion to fund a “drone transformation” of the armed forces, drawing on the lessons of the war in Ukraine.
– Some £11 billion on munitions and weapons to build up stockpiles and ensure the armed forces have the shells, bombs and missiles they need.
The Prime Minister said the Dip would ensure the UK would be ready to fight Vladimir Putin’s Russia by 2030 if necessary.
“We’ve learned a lot from Ukraine, actually also from Iran as well, about the capability that is needed in order to confront countries like Russia,” he said.
But General Sir Richard Barrons, a co-author of the 2025 strategic defence review, said the plan is “not going to crack the issue” of properly funding the nation’s armed forces.
Sir Richard told BBC Radio 4’s Today programme: “We’re not keeping up with our allies, we’re certainly not keeping up with our enemies, and we know that the US is no longer going to come and save European security in the face of a Russian threat.
“So until we come to terms with the fact that we have to find more money for defence sooner, and yes, it will be at the cost of other things we like more, we are simply not going to be ready to defend this country properly.”
Andrew Fox from the Henry Jackson Society security think tank said there is a “real danger” the wrong lessons were being learned from Ukraine as the Government focused on unmanned drone technology.
“Drones complement tanks, warships, combat aircraft, air defence, logistics and industrial capacity – they do not replace them,” he said.
“Using drones as a justification for avoiding the hard decisions on investing in Britain’s conventional military strength will leave the armed forces less prepared for future conflict.
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