John Healey resigned as Britain’s defense secretary on Thursday, directly criticizing Prime Minister Keir Starmer for what he described as insufficient military funding that leaves the country vulnerable in an increasingly dangerous global environment. Healey, a long-serving Labour politician and once one of Starmer’s closest allies, said he was informed early this week that Starmer planned to announce a defense investment plan falling short of the levels he deemed necessary.

In a resignation letter addressed to Starmer and posted publicly, Healey expressed deep concerns that the forthcoming Defense Investment Plan (DIP) would reduce armed forces readiness, increase risks to personnel deployed on operations, and ultimately undermine national security. Healey highlighted that the plan would raise military spending to 2.68 percent of gross domestic product by 2030, below the 3.0 percent target he and Starmer had previously discussed.

Starmer’s office released a response letter from the prime minister, defending the proposed defense funding as both sustainable and fair. Starmer underscored the need for responsible budgeting, emphasizing that maintaining strong public finances was essential to the country’s security and cautioning against excessive borrowing. The prime minister noted that the plan would require significant reallocations across government departments and would provide certainty to enable modernization of the armed forces, including investments in new technologies.

The resignation marks a major setback for Starmer, who faces growing internal party challenges ahead of a likely leadership contest this summer. Healey’s departure strengthens calls from party critics, such as Greater Manchester Mayor Andy Burnham, for a leadership change focused on shifting priorities toward domestic issues like health care and infrastructure, which some argue have suffered neglect amid defense spending debates.

Starmer’s government published a strategic defense review last year, aiming to enhance military capabilities with investments in long-range weapons, cyber command, drones, and undersea cable protection. In public comments last week, Starmer warned of Russia’s potential to launch an attack on NATO as early as 2030, underscoring the urgency of robust defense investment—comments Healey cited in his resignation as evidence of the prime minister’s awareness of defense needs.

Pressure to boost defense spending has also come from abroad, notably from former U.S. President Donald Trump, who has criticized Britain and European allies for underfunding their militaries. Yet Britain’s challenging economic environment complicates any significant military expenditure increase without politically contentious measures such as tax hikes, spending cuts in other sectors, or increased borrowing. Starmer faces criticism from his party’s left wing to prioritize investment in public services rather than defense.

In his letter, Healey attributed much of the funding impasse to Treasury officials, specifically pointing to Chancellor Rachel Reeves and her reluctance to commit resources amid competing budget priorities. Reeves has suggested that tax rises would be preferable to borrowing to finance defense, though Starmer’s position on this point remains unclear.

Government officials have remained tight-lipped about the details of the upcoming defense plan, which is expected before the NATO summit in early July. Conservative Party leader Kemi Badenoch accused Starmer of inaction at a time of increasing global threats, asserting that military projects are on hold and Britain’s defense capabilities are weakening. Starmer countered by citing increases in defense spending since the Conservative era and reiterated his commitment to publishing the investment plan.

Political analysts view Healey’s departure as particularly notable due to his reputation as a measured, pragmatic politician. Tony Travers, a politics professor at the London School of Economics, described Healey as a “rational moderate” unlikely to resign lightly, suggesting the defense funding dispute deeply fractured the prime minister’s team.