The UK defence spending target of 3% of GDP by 2030 is the number John Healey cannot keep deferring, and the bond market is running out of patience with the pretence that he can. Whatever reassuring language emerges from Monday’s growth speech, the arithmetic at the Treasury has become unforgiving.
Healey resigned as shadow defence secretary in June over precisely this issue. His return to government as chancellor was widely read as a personal commitment to hitting 3% by 2030. Yet Treasury sources now suggest the timeline will be deferred to next year’s spending review. That is a political risk as well as a fiscal one: six more months of speculation about the defence budget is exactly what destabilised his predecessor’s tenure at No 11.
The UK Defence Spending Target No One Is Costing Honestly
The scale of the commitment is rarely stated plainly. the Royal United Services Institute calculated that reaching 3% of GDP on defence by 2030 would require a real-terms increase in the defence budget of around 60%, equivalent to roughly £157 billion in additional spending over eight years compared with prior planning assumptions. That would be the largest expansion of British defence spending since the early 1950s.
The Institute for Fiscal Studies adds its own sobering context. The July 2025 Spending Review allocated defence spending of 2.6% of national income in 2028-29, just 0.3 percentage points above the 2024-25 level. At the NATO Summit in The Hague in late June 2025, the government committed to reach 3.5% by 2035, but specified no path to get there. The IFS identifies a range of scenarios, from steady topping-up of the Spending Review allocation to deferring all increases beyond 2.6% until after the next election. The gap between those paths could run to tens of billions.
A Green Alliance analysis puts a sharper figure on the immediate problem: bringing 3% into the current parliamentary term would require roughly £10 billion more, on top of the £10 billion in cuts already pencilled into unprotected departmental budgets by 2029-30 to meet existing fiscal rules. Helen Miller, director of the IFS, made the same point to the Guardian: ‘If the government knows for sure… that they want to increase defence spending to 3% by the end of the parliament, that would mean that to stick within the current plans, you’d have to hold all other departments, including the NHS, flat.’ She added: ‘that seems pretty unlikely.’
Gilt Yields Are Doing the Talking
The bond market is not waiting for a spending review. According to the Office for Budget Responsibility’s November 2025 Economic and Fiscal Outlook, the 10-year gilt yield stood at 4.8% and the 20-year at 5.6%, with market participants pricing in a further rise to 5.8% on the 10-year by 2030. The Resolution Foundation’s Q3 2025 Macroeconomic Policy Outlook recorded the 30-year gilt yield reaching 5.9% during summer 2025 market moves, its highest level since 1998.
Those yields have consequences for spending. The OBR’s November 2025 outlook showed cash spending in 2025-26 running £23 billion higher than the March forecast, with debt interest alone accounting for £2.4 billion of that overshoot. Welfare spending added £7 billion; local authority pressures a further £6 billion.
The erosion of fiscal headroom is the immediate political problem. The Lords Library reports that Bloomberg estimates suggest recent rises in borrowing costs may have halved the OBR’s November 2025 fiscal headroom of £22 billion. The Resolution Foundation puts the remaining headroom even lower, at around £8 billion. Borrowing figures for the four months to July 2026 showed the government had already overshot the OBR’s March 2026 forecast by £2.3 billion.
Against that backdrop, ING analysts note that UK gilt issuance is expected to remain perilously close to £300 billion in the current fiscal year and the same again in the next, according to the Debt Management Office’s remit. Healey returned from the G20 finance ministers’ meeting in Asheville with gilt market volatility as a central theme. He knows the pressure.
The case for deferral is understandable: lock in a headline of stability, buy time for the spending review, hope the gilt market calms. The case against is stronger. Delay does not make the arithmetic easier. Every month of procrastination on the UK defence spending target allows speculation to harden into market anxiety, which in turn erodes the very headroom the Treasury needs to act. Healey was right the first time, when he called for a ‘headmark date’ of 2030. The budget is where he should say so again, costs and all.
