Sir Keir Starmer has resolved to push Britain’s defence spending higher and faster than current government plans require, with sources at 10 Downing Street confirming to Bloomberg that the decision has effectively been made and that the mechanics of implementation are being worked through at senior levels.
The move carries as much political calculation as it does strategic intent, coming less than a month before local elections on May 7 that are widely expected to deliver heavy losses for the Labour Party and potentially trigger a formal leadership challenge.
The strategic backdrop is stark. Britain’s Chief of Defence Staff confirmed this week that the government is updating its Government War Book — the classified national continuity plan last seriously revisited during the Cold War — to prepare civilian infrastructure, the police, industry, and the NHS for the possibility of high-intensity conflict.
The confirmation came at the London Defence Conference, where the defence chief also revealed that a threat from the UK to seize vessels in Russia’s shadow fleet was already altering behaviour before British forces had boarded a single ship.
Separately, Defence Secretary John Healey revealed that British warships and aircraft had spent roughly a month monitoring three Russian naval vessels — an Akula-class attack submarine and two specialist GUGI deep-sea research submarines — operating off the UK’s northern coast before they withdrew.
Retired General Sir Richard Barrons, who contributed to the government’s Strategic Defence Review, has been among the most vocal voices pressing for greater urgency, publishing an article arguing that Britain must “act today” with a sustained increase of approximately £10 billion per year in defence funding.
He described the UK armed forces as having been “hollowed out” by decades of underfunding and warned that the country “can no longer rely on the US cavalry to bail us out,” a reference to the deterioration of UK-US defence certainty under the Trump administration. Barrons estimated that a three-to-five-year window exists to address the most critical capability gaps, a timeline he described as tightening fast.
The fiscal challenge is the central complication in all of this. The government has committed to spending 2.5% of GDP on defence by 2027 and 3.5% by 2035, as part of a NATO agreement reached last year, but the Treasury has made clear that any acceleration beyond current plans will require either tax increases or cuts to other departmental budgets, without breaching borrowing rules. The Institute for Fiscal Studies has noted that existing defence spending plans are already squeezing non-defence budgets in 2026-27 and 2027-28, and that further acceleration would compound those pressures materially.
Adding complexity is the fact that the government’s long-promised Defence Investment Plan — a ten-year document intended to show industry how military spending will be allocated — remains unpublished despite having been promised in autumn 2025 and then again by Christmas.
The delay has left defence companies in a form of commercial limbo, with some start-ups relocating abroad and at least one Business winding down its defence arm while waiting for government contracts to clear. Until the plan is published, much of the additional funding commitment remains theoretical, even as the political language around it escalates.
Starmer’s calculation appears to be that a visible commitment to national security — particularly given the unresolved US-Iran conflict and Russia’s sustained hybrid campaign against European undersea infrastructure — provides the most credible narrative to stabilise his position ahead of local elections. Whether it proves sufficient will depend partly on whether the May results are bad enough to move Labour MPs to formally back a single challenger, which requires 80 signatures to trigger a leadership contest. At the moment, no challenger has consolidated that level of support, but the local election results will recalibrate those calculations overnight.