Britain's defense secretary and armed forces minister quit Thursday in a disagreement over military spending, piling pressure on beleaguered Prime Minister Keir Starmer, who is facing calls to step down.

Defense Secretary John Healey resigned, warning that Starmer's long-awaited Defense Investment Plan (DIP), which outlines military funding for the next decade. — which the leader has yet to publish — risked making Britain "less safe."

In the evening, Al Carns became the second senior figure in defense to quit, resigning as armed forces minister, along with Healey aide Pamela Nash.

The resignations weaken Starmer's authority at a precarious moment, a week before a by-election that could prompt a bid to replace him.

"You have been unable, and the Treasury has been unwilling, to commit the resources that the nation needs to defend the country at this time of rising threats," Healey wrote in a resignation letter to Starmer posted on his X account.

"After explaining to you that I would not be able to accept a DIP settlement that does not give our Forces the resources they need, I am now left with no other option than to submit my resignation."

Former army officer Dan Jarvis was named as Healey's replacement, moving from a junior ministerial post at the Home Office.

"My first duty is to keep the British people safe, and I will always do what is necessary to protect our national security," Starmer said after Jarvis's appointment.

"This Labour Government is delivering the largest sustained increase in defense spending since the Cold War," he said.

"In a dangerous and volatile world, we will give our armed forces the capabilities they need to defend Britain and keep our nation secure."

The defense plan has been repeatedly delayed but Starmer has insisted he will publish it before a NATO summit in Turkey on July 7.

Starmer's center-left government, elected in July 2024 after 14 years of Conservative rule, has pledged to raise spending and prioritize NATO, as the threat from Russia grows.

President Donald Trump has repeatedly urged NATO allies to spend more and become less reliant on Washington for security.

'Grave moment'

Starmer has vowed to raise defense spending to 2.5% of economic output from next year, increasing to 3% if Labour wins the next general election, expected in 2029, before reaching 3.5% in 2035.

But media reports have suggested discontent behind the scenes over the specifics of the spending plan.

Healey said in his letter he was first given full sight of the DIP on Monday and it sees defense spending rise to only 2.68% of output in 2030.

A source close to the former defense secretary told AFP the deal offered by the finance ministry did not put a date on the 3% commitment.

The plan fell "well short of what is required" for defense and the country, Healey wrote.

Tory leader Kemi Badenoch said Starmer's "premiership is falling apart."

Starmer faces political peril in next Thursday's contest when Greater Manchester Mayor Andy Burnham stands for the Makerfield parliamentary seat in northwest England.

Burnham has said he would participate in any Labour leadership race, although none has yet been triggered.

Wes Streeting quit as health secretary last month following disastrous local and regional election results for Labour and has said he would run in any future contest.

Healey has been mentioned as another potential contender, but there was no immediate suggestion that his resignation is linked to the leadership speculation.

The investment plan, originally due to be published in late 2025, has repeatedly been pushed back, to the frustration of industry and others.

Healey's resignation "creates a sequence of political headaches," starting with finding a new minister and then trying to get the investment plan published, said Ed Arnold, senior associate fellow at the RUSI think tank.