Starmer called the GBP300 billion figure a "record investment" that would transform Britain's military, as the nature of modern warfare changes.

"By any measure, this is a huge historic shift for our nation and a legacy in which I take pride," he told reporters.

Starmer is expected to leave office next month after losing the support of Labour members of parliament and urged likely successor Andy Burnham to see through his defence spending commitment.

"I am absolutely certain that this is the platform on which whoever comes after me can build," Starmer added.

The plan follows months of wrangling within the Labour government over the resources required to modernise Britain's fighting capabilities, to counter greater aggression from countries such as Russia, and mitigate for a less reliable United States.

Two defence ministers quit earlier this month in a row over the defence plan, including defence secretary John Healey who said it risked making Britain "less safe".

The resignations highlighted Starmer's weakening authority.

He announced on June 22 he was stepping down after MPs from his ruling Labour party switched their support to veteran politician Burnham.

Burnham, the 56-year-old former Greater Manchester mayor, will take over as prime minister in mid-July if he faces no challengers for the Labour leadership.

'Hybrid' vessels

Starmer's plan includes more than GBP5.0 billion for drones and autonomous systems over the next four years, the Ministry of Defence (MoD) said in a press release.

The investment will see capabilities ranging from "highly complex autonomous mine-hunting drones to small 'quadcopter' tactical drones, and low-cost 'kamikaze' one-way attack drones", the MoD added.

The wars in Ukraine and Iran have highlighted the increased use of war-fighting robots.

Ukraine uses roughly 200,000 drones a month to defend itself from Russia's invasion, while at the height of the US-Israel-Iran conflict 700 offensive drones were being launched per day, the MoD said.

The plan seeks to develop a "hybrid" Royal Navy by replacing six ageing destroyer warships with smaller, autonomous vessels working alongside crewed ships.

It also allocates more than GBP8 billion to create the next generation of stealth fighter jet alongside Italy and Japan, and a $64 billion upgrade to Britain's nuclear deterrent.

Starmer, who had already cut the international aid budget to boost defence spending, said cuts to road and energy projects would help pay for the new uplift.

US President Donald Trump has demanded that NATO members spend five percent of economic growth on defence by 2035 and become less reliant on Washington for security.

Starmer said the defence plan will take defence spending to 4.2 percent of gross domestic product, but did not specify a date.

The GBP15 billion uplift is well short of the GBP28 billion that military leaders previously said was needed.

NATO Secretary General Mark Rutte welcomed Starmer's plan.

"Stronger UK defence makes us all safer," he wrote on X.

But the opposition Conservatives' defence spokesperson, James Cartlidge, said the plan was "too little, too late".

"The plan is now almost a year overdue and only being rushed through because Keir Starmer is desperate for a legacy," he added.

Bence Nemeth, a defence studies lecturer at King's College London, said that while the announcement was "an improvement" it was "clearly not enough", noting that most of the money was going to major projects already in the pipeline rather than new capabilities.

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