The UK defence secretary for almost the last two years, John Healey, has resigned amid the continued wrangling within the UK government over the need to raise defence spending and by how much.

In his resignation letter, submitted to UK Prime Minister Sir Keir Starmer on 11 June 2026, Healey outlined how a clear requirement to substantially raise UK defence spending on national security grounds has been scotched by active resistance from the UK Treasury and a prime minister not politically strong enough to see those plans through.

“We came into government, recognising Britain faced a new era of threat which demanded a new era for defence,” Healey wrote. “The SDR (Strategic Defence Review) we jointly commissioned set the 10-year vision to transform our Armed Forces, strengthen alliances, invest in the technology that is changing warfare and back British industry to make defence an engine for growth,” Healey wrote.

“This new era for defence required further investment through the Defence Investment Plan (DIP),” Healey continued. “The excellent and extensive cross-government work that completed in January – overseen by you, me and the Chancellor – confirmed the scale of the challenge and the rising demands on defence.

“Since then, you have been unable, and the Treasury has been unwilling, to commit the resources that the nation needs to defend the country at this time of rising threats.”

The specific event that led to Healey’s resignation appears to have been his first viewing on 8 June of a final draft of the DIP, which was originally promised for the autumn of 2025 but has most recently been expected to emerge in public just prior to the NATO summit in Ankara, Türkiye, in July.

Healey told Starmer that “your DIP financial settlement – which I was first given in full on Monday afternoon this week – falls well short of what is required for defence and the country at this dangerous time. The extra support is backloaded when the pressure of operations and imperative to speed up readiness to fight is in the first two years and it rises to just 2.68% of GDP in 2030, when we will reach 2.6% next year with the investment we are already making.”

Warning of the prospect that NATO Europe could face direct conflict with Russia as early as 2030, Healey has been adamant that UK defence spending needs to reach a level of 3% of GDP by that point. Indeed, Starmer himself pledged on 23 June 2025, on the eve of the NATO summit in The Hague, that UK defence spending would reach 3.5% of GDP by 2035. Since then, of course, national finances globally have been buffeted by the US Trump Administration’s tariff wars and more seriously damaged by the US/Israeli war against Iran and the consequent choking of international shipping in the vital Strait of Hormuz.

This will have made increasing defence spending – which is hardly ever a vote-winning policy politically – even harder, although Healey fully acknowledged in his resignation letter that difficult choices would have to be made.

“In funding the DIP I fully recognise the strain this places on colleagues in other Departments, both now as you have required spending switched into defence and in the future. I am very grateful to those colleagues who have supported this, and I appreciate how difficult their choices will have been,” he wrote.

Yet Healey continued to believe there were “credible ways of meeting the mid-term funding challenges” that the UK Treasury has apparently blocked, with Starmer failing to overrule that.

Black holes and wastefulness

There are essentially two main issues that blight UK defence spending: the first is that there has for decades been a disconnect between what the UK government says it needs to be able to accomplish with its armed forces on the world stage and what it is prepared to budget for to accommodate those aspirations; the second is the fact that the UK Ministry of Defence (MoD) continues to be incredibly wasteful with the budget that it does have – and thus gets considerably less ‘bang for its buck’ compared to other European countries.

Inadequate UK funding for defence means there is invariably a financial ‘black hole’ representing the shortfall between what is required to achieve the UK’s defence capability aspirations and what the armed forces actually receive in funding.

The MoD’s current black hole is widely assessed to be GBP 28 billion (EUR 32.4 billion). While Healey had pushed to secure a minimum GBP 18 billion extra in defence funding over the next four years, it appears that the DIP draft he reviewed on 8 June offered up just GBP 10 billion.

“Without a DIP that meets the moment in this way, I am being forced to make decisions that would reduce the readiness of our Forces and increase the risk to personnel on operations, and could make the country less safe,” Healey wrote. “After explaining to you that I would not be able to accept a DIP settlement that does not give our Forces the resources they need, I am now left with no other option than to submit my resignation as your Defence Secretary.”

In the wake of Healey’s resignation UK Armed Forces Minister Al Carns, a decorated former colonel in the Royal Marines and thought by some as a potential Labour Party leader, told Times Radio that the DIP was “not fit for purpose” and that Starmer “has got to sort it out”.

Later in the day Carns also resigned. In a resignation statement that could also be seen as a pitch for any leadership contest against a beleaguered Starmer, Carns stated, “While I had no hand in the Defence Investment Plan, that distance does allow me to say plainly that it is not built for the threat we face. It is neither transformative enough nor sufficiently funded. We are asking our Armed Forces to operate in a more dangerous world on a budget written for a calmer one.”

Meanwhile, Dan Jarvis, a former British Army officer who has served as security minister since 2024 and a Cabinet Office minister since 2025, has been appointed as the UK’s new defence secretary.

Not enough output focus

A key issue with the development of UK defence capabilities, regardless of how much funding is input through the defence budget, is that there is not enough focus on output of actual defence capability at the other end.

The UK MoD’s 1998 Strategic Defence Review (SDR), for example, introduced defence planning assumptions. These were constructed around a scale-of-effort baseline for expeditionary operations that went beyond the UK armed forces’ day-to-day capabilities. By 2015, however, the UK Strategic Defence and Security Review (SDSR) featured considerably less detail on defence planning assumptions.

In a positive move towards closing the gap between UK capability aspirations and actual defence funding, the 2025 Strategic Defence Review (SDR) moved away from a focus on the UK military’s ability to act on the world stage. Instead, the 2025 SDR emphasised a NATO-first doctrine alongside an assumption that the UK armed forces would not fight in a ‘peer-level’ conflict alone.

However, while the 2025 SDR made it perfectly clear that the UK, alongside its European allies, faced a clear and present threat from Russia, especially in light of the UK’s support for Russia-invaded Ukraine, the UK’s Labour government appeared to be dragging its heels on taking that threat seriously – especially regarding the absence of a DIP. Thus on 14 April 2026 Lord Robertson – a former UK defence secretary, former NATO secretary general and the SDR’s chief co-author – felt compelled to speak out.

“I spent the best part of a year working on the new government’s Strategic Defence Review, and I can tell you now, bluntly, the conclusion of all of that work. We are underprepared. We are under-insured. We are under attack. We are not safe. Bluntly, that is the underlying message that we got,” he stated.

Lord Robertson warned in his speech that the US/Israeli conflict with Iran, and the consequent disruption to global supply chains, “has to be a rude wake-up call to this country. On top of what we’ve already seen in Ukraine, it should remind us in the United Kingdom of our vulnerabilities, and there are many.”

Lord Robertson further warned, “There is a corrosive complacency today in Britain’s political leadership. Lip service is paid to the risks, the threats, the bright red signals of danger, but even the promised national conversation about defence can’t be started.”

Ultimately it is clear that the 2025 SDR’s authors and the defence secretary they delivered it to are of the same mind.