The UK Secretary of State for Defence John Healey resigned from his post on 11 June, having issued his letter of resignation on the social media platform X in which he criticised the proposed financial settlement for the Defence Investment Plan.

In it, Healey blamed the Treasury, which he said was “unwilling” to allocate sufficient funds to defence, made worse by the inadequate backing of the UK Prime Minister Keir Starmer, who he said was “unable” to make the necessary commitments.

It appears that Healey was finally prompted to resign after reviewing Starmer’s financial settlement for the long overdue and routinely delayed Defence Investment Plan (DIP) on Monday this week, saying the settlement “falls well short of what is required… at this dangerous time.”

The DIP is intended to provide a cost breakdown of the priority defence programmes for the next ten years; it is informed by the recommendations put forward in the Strategic Defence Review in June last year.

In recent weeks, as the Government has hinted the imminent release of the document, defence observers have speculated that the funding will range between £12-18bn - still well below the £28bn ($33.4bn) shortfall needed to pay for all desired programmes.

Moreover, Healey confirmed that Starmer’s settlement was so low that he was being “forced” to make decisions that “would reduce the readiness” of forces and “increase the risk to personnel on operations,” without specifiying the capabilities absent from the final settlement.

It is ironic that the Treasury should draw back its fiscal support for the defence and security space given previous claims that the Government intend to make “defence an engine for growth,” as the mantra goes.

Senior RUSI associate fellow Ed Arnold described Healey's resignation as a "seismic moment" for the UK Government. The move will ensure officials "find it harder to be complacent on defence spending."

Unite, a leading trade union representing British defence workers, has repeatedly expressed concern that chronic underfunding and successive delays in Whitehall risk specialist skills in the sector. General Secretary Sharon Graham remarked that "scrabbling around robbing Peter to pay Paul on such a critical plan is embarrassing and a sign of weakness."

Conservative James Cleverley, former Foreign Secretary, welcomed the decision, which he said proved that Healey took defence “more seriously” than either Keir Starmer or the Chancellor Rachel Reeves.

Late on 11 June, Armed Forces Minister Al Carns also resigned his post, stating in his announcement post on X that "Number 10 [Downing Street] will not listen".

Dan Jarvis, former Minister of State at the Home Office, has been announced as the new UK Secretary of State for Defence.

This article has been updated to reflect other views as the development unfolds.