The Defence Investment Plan: Too Little, Too Late, and Too Slow for Britain’s Defence Needs

By Mark Allatt, UK Defence First

The publication of the Defence Investment Plan (DIP) at the end of June 2026 has been presented by the government as a significant step forward in addressing the challenges facing the United Kingdom’s armed forces. With an additional £15 billion committed over four years, ministers speak of warfighting readiness, hybrid capabilities, and a modernised force structure better suited to contemporary threats. Yet, the plan represents a profound disappointment. It fails to place Britain on a firm trajectory towards spending 3 per cent of GDP on defence, let alone the sustained 5 per cent commitment that is essential for credible national security in an increasingly dangerous world.

The DIP does not reverse the corrosive hollowing out of the services. Instead, it doubles down on an over-reliance on unproven autonomous systems while cancelling or deferring vital crewed platforms, underfunding support infrastructure, and offering only vague commitments on industrial capacity. When compared with the consistent and ambitious investments being made by nations such as Germany, Poland, South Korea, and Japan, Britain’s plan appears hesitant and inadequate.

At its core, the DIP provides incremental funding within constrained budgets rather than the transformative increase required. Core defence spending currently sits at around 2.3 per cent of GDP, with a target of 2.5 per cent (or 2.6 per cent including intelligence) by 2027 and only conditional ambitions for 3 per cent thereafter - around 20% of this budget is spent on the independent nuclear deterrent. The additional £15 billion does little to close the substantial funding gap - estimated by military chiefs at nearer £28 billion - that has delayed meaningful progress. Only a defence-first approach to public spending, with resources redirected from areas such as welfare, foreign aid, and net zero, can deliver the necessary resources without damaging economic stability. Anything less leaves Britain dependent on allies and vulnerable to peer adversaries.

Shortcomings Across the Royal Navy

Nowhere is the DIP’s shortfall more evident than in the Royal Navy. The centrepiece of the naval element is the shift to a “hybrid navy,” in which new Common Combat Vessels serve primarily as crewed hubs directing swarms of uncrewed air, surface, and underwater drones. While innovation in autonomous systems has value, this represents over-reliance on such technology at the expense of traditional hulls. The cancellation of the Type 83 destroyer programme is particularly concerning. These vessels should be the foundation of a Future Air Dominance System, hardened for operations in demanding environments such as the High North and equipped for integrated air and missile defence alongside long-range precision strike. Their replacement with lighter CCVs risks leaving the fleet without sufficient high-end escort capacity once the Type 45s reach the end of their service lives.

This decision compounds existing weaknesses. The plan offers no accelerated drumbeat for Type 26 and Type 31 frigate construction, despite the urgent need to rebuild the escort fleet towards a target of around 24 vessels by the mid-2030s (as recently as 1997 they numbered at least 35). There is scant detail on how the ambitious programme for 12 AUKUS submarines can be delivered on a realistic timeline, given current industrial infrastructure limitations and the fact that no Astute-class submarine is currently available for operational deployment. Such gaps in submarine availability undermine the UK’s contribution to NATO and its own strategic deterrence.

Furthermore, the DIP fails to address critical enablers for carrier operations. The absence of organic airborne early warning aircraft for the Queen Elizabeth-class carriers leaves strike groups exposed, with limited progress to-date on solutions such as carrier-compatible variants of the MQ-9B drone. Broader personnel challenges, including acute recruitment and retention difficulties across the Navy, receive insufficient attention. Without addressing pay, housing, and career structures, even the most advanced platforms will lack the crews needed to operate them effectively.

Challenges Facing the Royal Air Force

The Royal Air Force fares little better under the DIP. The plan includes investment in F-35A aircraft, which supports certain NATO nuclear mission requirements but comes at the expense of additional F-35B orders essential for fully equipping both aircraft carriers and on top of the existing shortfalls in the F-35B fleet, including numbers, weapons integration, infrastructure, and trained personnel. Prioritising the conventional take-off and landing variant over carrier-optimised aircraft weakens one of Britain’s most potent strategic assets.

Air-to-air refuelling incompatibilities continue to hamper operational flexibility, limiting the RAF’s ability to project power at range with numerous essential platforms having to rely on allies for refuelling or severely limiting their operational effectiveness. Procurement remains limited to three E-7 Wedgetail airborne early warning aircraft, falling short of the five that many analysts regard as necessary for adequate coverage - the UK even has the radars for an additional two which were purchased before the reduction in numbers. The run-down of the transport fleet adds further strain. The premature retirement of the Hercules has not been adequately offset by sufficient additional Voyagers, A400Ms, or C-17s, constraining the RAF’s ability to move troops and equipment rapidly in crisis situations, especially in a tactical environment.

These gaps occur against a backdrop of broader recruitment and retention problems that affect pilot and ground crew availability. The DIP offers little in the way of concrete measures to resolve them. Meanwhile, space capabilities receive minimal detailed attention, despite the growing importance of this domain for communications, navigation, and intelligence. The plan fails to fund a more ambitious sovereign approach to space resilience, including multi-orbit systems.

Pressures on the British Army and Cross-Service Issues

The British Army faces its own set of challenges under the DIP. While there is emphasis on drones, loitering munitions, and uncrewed ground vehicles, there remains a requirementfor balanced investment that maintains heavy armour and protected mobility. The lack of commitment to additional Challenger 3 tanks leaves the Army short of the mass required for high-intensity land operations. Helicopters remain insufficient across all three services, compounding mobility limitations for the Army, support for special forces, and joint operations more broadly. Earlier reductions in programmes such as the New Medium Helicopter have already created shortfalls; the DIP does not reverse this trend.

Recruitment and retention issues cut across all services and represent one of the most acute failures. Substandard forces housing continues to damage morale, despite earlier government promises of a substantial refurbishment programme. Investment in the cadet forces, vital for inspiring the next generation, appears constrained or reduced at a time when the services desperately need a stronger pipeline of talent. An army of at least 82,000 regulars, ideally closer to 90,000, alongside a robust reserve, is the minimum credible force level. The DIP does not provide the funding or policy focus necessary to achieve this.

Homeland air and missile defence receives some allocation, consistent with signals in the Strategic Defence Review, but falls well short of the integrated, layered system necessary toprotect critical infrastructure against missile and drone threats. Munitions production sees welcome but limited attention, with calls for six new factories only partially addressed.

International Contrast and the Path Forward

Britain’s hesitant approach stands in sharp relief against the actions of key allies and partners. Poland has pursued one of the most ambitious defence build-ups in Europe, significantly increasing spending as a share of GDP to almost 5% and investing heavily in artillery, tanks, aircraft, and air defence in response to the Russian threat. South Korea maintains a robust modernisation programme, balancing advanced indigenous systems with high volumes of capable platforms to deter North Korea while contributing to regional stability. Japan has steadily raised its defence budget, investing in missiles, ships, aircraft, and space capabilities as it strengthens its alliance with the United States and partners in the Indo-Pacific. Even Germany has recently increased defence spending by over 20% and has committed to achieve 3.5% of GDP by 2029. These nations demonstrate the political will to match rhetoric with resources. The United Kingdom must do the same.

In summary, the Defence Investment Plan is too little in funding scale, too late in addressing long-standing capability gaps, and too slow in its industrial and recruitment timelines. It leans excessively on drones and hybrid concepts without the foundational crewed mass, support enablers, and personnel foundation that are indispensable. Greater ambition is required: accelerated shipbuilding, additional F-35Bs and Typhoon sustainment where needed, a larger helicopter fleet, robust submarine and munitions industries, proper investment in air and space domains, and decisive action on recruitment through improved housing, pay, and cadet programmes.

The incoming Prime Minister must recognise that Britain cannot afford further delay. A genuine defence-first budget, funded through sensible reprioritisation, is the only way to restore the United Kingdom’s place as a serious military power capable of deterring conflict and defending its interests. The DIP falls short of that standard. The nation deserves - and its security demands - better.