The Starmer Defence Investment Plan has arrived as a defining moment for the outgoing prime minister, promising billions of pounds for Britain’s armed forces while quietly handing his successor an unenviable financial burden. In cementing what he hopes will be a legacy as a global statesman, Keir Starmer has effectively tied the hands of Andy Burnham, who is poised to inherit the task of paying for it all.

The plan represents both a bold statement of intent and a source of lingering frustration over what it leaves unfinished.

A Landmark Announcement

Starmer’s speech unveiling the Defence Investment Plan, or DIP, is likely to stand as the last major policy he announces before stepping down. Burnham is all but certain to take over as leader within three weeks, making this a parting act as much as a governing one.

The plan commits an additional £15 billion to the armed forces to confront the greatest threats facing the United Kingdom. Of that, £5 billion is earmarked for autonomous systems such as drones and uncrewed vehicles. With these additions, the defense budget now approaches £300 billion over the next four years.

Part of that total includes an extra £1.5 billion in new money secured by Defence Secretary Dan Jarvis on top of the original proposal, a late addition that prompted his predecessor, John Healey, to resign in protest.

The Problems Left Behind

For all its ambition, the plan carries significant gaps. Most notably, it offers no clear funding pathway to reach the U.K.’s NATO target of 3.5 percent of GDP by 2035, and it contains no commitment to produce one before the next general election, scheduled for 2029.

The numbers illustrate the shortfall starkly. Britain will reach 2.7 percent next year, but that figure will not climb again before 2030. Should he become prime minister, Burnham will have to use his very first budget to find nearly £5 billion to fund Starmer’s plans, and his first spending review to locate billions more to honor Britain’s promises to NATO allies.

Critics were quick to seize on the shortfall. Andrew Kinniburgh, director-general of Make UK Defence, argued that while many European allies are racing to meet the new NATO target years ahead of schedule, the U.K. is stuck on the go-slow.

Burnishing a Legacy

Starmer used the occasion to spotlight what he sees as his signature achievements on the world stage. He highlighted the coalitions he helped assemble to support Ukraine and to stabilize the situation following the Iran conflict, and he boasted of delivering the biggest sustained increase in defense spending since the 1980s.

In doing so, he not only outlined what he believes Burnham’s international priorities should be but even prescribed how they should be met. Yet the moment also drew attention to a central frustration of his time at No. 10: while he pushed national security up Labour’s agenda, he struggled to match the pace at which Britain’s allies have rearmed.

A Measure of Relief for Industry

Despite the criticism, the plan’s arrival brought genuine relief to defense companies and service personnel. After ten months of uncertainty, many welcomed the sense of direction, even as debates over funding levels continued.

Kevin Craven, CEO of ADS, which represents more than 2,000 firms in the sector, said the clarity would help the U.K. defense industry do what it does best, supplying the equipment, capabilities, and services that underpin national security. The certainty allows businesses and strategists to finally make decisions after months in limbo.

Still, few pretended the price tag told the whole story. Speaking at a drone manufacturer’s headquarters in Berkshire, Starmer called the DIP a massive step forward while acknowledging he had no road map for reaching 3 percent of GDP, insisting only that it must be the top priority at the next spending review.

Doubts From Within

That admission drew pointed responses, including from Healey, who had quit partly over the refusal to chart a course toward Britain’s spending pledges. He argued the country needs both a target date for 3 percent and a credible funding plan to meet the 3.5 percent NATO commitment by 2035, warning that European security itself is at stake.

The unease extended across the Labour Party and the defense sector. One Labour MP with a close interest in defense, speaking anonymously, allowed that the strategy moves things forward but insisted much more needs to happen, a burden that will now fall to Burnham. A defense industry representative was blunter still, calling it ludicrous that Starmer could warn that Russia might be ready to invade a NATO country by 2030 while failing to commit to 3 percent by that same year.

Ed Arnold, an associate fellow at RUSI, offered a similar verdict, describing the plan’s modest uplift to around 2.7 percent by 2029 as merely deferring a massive financial injection into defense.

Passing the Financial Buck

Starmer also sketched out what he believes Burnham should prioritize in his first spending review, a major Treasury exercise conducted every few years, while firing a warning shot at alternative financing options reportedly under consideration.

The DIP explicitly names defense as the number one priority at that next review, even though it will almost certainly be presented by a new chancellor rather than Rachel Reeves, who stood alongside Starmer at the launch. The prime minister cautioned against the idea of so-called war bonds, floated by former Bank of England economist Andy Haldane, now advising Burnham, warning they would push interest rates higher at a time when one pound in every ten already goes toward servicing debt.

Notably, Starmer made no mention of the Canadian-backed Defense, Security and Resilience Bank, fueling speculation that the U.K. will not join as a founding member at next week’s NATO summit, despite a push from Burnham’s team for London to sign on. The Treasury has allocated just £400 million to a separate Multilateral Defence Mechanism, a proposal from the U.K., Finland, and the Netherlands, amounting to roughly half the entry requirement for the larger bank.

The Bill Comes Due

Perhaps most pressing for Burnham is the fine print buried in the plan. It stipulates that £4.7 billion must be found in savings at the next budget, most likely through cuts to other departments, with £1.8 billion of that front-loaded into the current financial year.

Allies of Burnham said he had been briefed on the DIP and supports it, though they declined to explain how he intends to hit the targets that eluded Starmer. One person close to him said Burnham recognizes the rising demands on defense and has been clear about the need for investment that unambiguously backs British jobs and British industry.

As Starmer prepares to exit, his defense plan stands as a fitting emblem of his tenure: ambitious in vision, statesmanlike in framing, yet leaving the hardest financial questions for someone else to answer. For Burnham, the challenge is now unavoidable, and the clock is already ticking.