What's happened to UK defence spending?
In his resignation letter former Defence Secretary John Healey said the UK's defence investment plan (DIP) "falls well short of what is required for defence and the country at this dangerous time".
The plan - which has yet to be published - will explain how new equipment and defence infrastructure will be funded over the coming decade and follows the wide-ranging Strategic Defence Review published on 2 June 2025.
But in his letter to the prime minister, Healey says Sir Keir Starmer is "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".
The letter suggests the planned DIP intends to increase defence spending in 2030 to 2.68% of GDP.
That implies an 0.08% increase on the existing 2027 commitment of 2.6% of GDP - around £2.4bn in today's money.
Healey's letter says the government should aim to spend 3% of GDP on defence by 2030."
BBC Verify has been looking at the current size of the UK military.
What has happened to the size of the armed forces?
In 1990 - at the end of the Cold War - the army had 153,000 regular soldiers in its ranks, this is now down to 73,790.
The 2025 SDR recommended that the British Army's regular force should not drop below 73,000.
In its latest update, the Ministry of Defence (MoD) confirmed the number of people applying to enlist in the regular army had fallen by around 40% in 2025 compared to 2024.
Since 1990, the number of reservists has fallen from 76,000 to 25,770.
In 1990, the Royal Navy had 48 major combat ships (13 destroyers, 35 frigates).
That has dropped to seven frigates and six destroyers.
There has been criticism of the Navy's readiness after it took weeks to deploy a single ship - HMS Dragon - to the Gulf to help protect an Royal Air Force (RAF) base in Cyprus.
In 1990, the RAF had over 300 combat jets.
Now, with 107 of the newer model Eurofighter Typhoons and at least 37 Joint Strike Fighter F-35 Lightning II in service, it has far fewer, though they are technically superior.
Uncrewed aircraft systems, also known as drones, now form an element of the UK's military air capabilities. These did not exist in 1990.
The threat from drones has been highlighted in the Ukraine conflict where they now kill more people than traditional artillery.
Analysts say the UK needs to invest considerably more in this military technology.
Former Nato chief warns UK's national security 'in peril'
Criticism of complacency on defence spending will sting government
The government has said it is planning "the largest sustained increase in defence spending since the Cold War".
But that is a low bar because defence spending has been on an almost constant downward path since the fall of the Berlin Wall.
The government is currently planning to commit 2.5% of GDP to Nato-qualifying defence spending by April 2027 (2.6% including spending on the security and intelligence services) with an "ambition" to spend 3% of GDP in the next Parliament.
In April, Lord Robertson, who led the government's recent Strategic Defence Review, said: "We cannot defend Britain with an ever-expanding welfare budget."
Spending on working-age benefits was lower than on defence in the mid 1980s - but now it's more - and is projected to rise to around 4.3% of GDP by the end of the decade, pushed up, in part, by rising claims for things like Personal Independence Payments (PIP).
While there is some evidence that a rising number of people suffering from mental health conditions have contributed to the increase in PIP claims, independent researchers remain uncertain about the exact causes behind the upward trend.
How does UK defence spending rank in Nato?
In addition to the "ambition" to spend 3% of GDP on defence during the next Parliament, the UK has committed to a Nato target to spend 5% of GDP on "national security" by 2035.
The government has said this would be made up of 3.5% of GDP on "core defence" and another 1.5% of GDP going on things like protecting critical infrastructure and ensuring civil preparedness.
Only three countries: Poland, Lithuania and Latvia, spent more than 3.5% of their GDP on defence in 2025, although Estonia and Norway were close.
The UK's spending of 2.3% of GDP in 2025 put it just above the mid-point of spending by Nato members, according to figures from the military alliance.
How much do Nato members spend on defence?
What is the UK military's record on big spending projects?
The MoD has some of the largest procurement projects in government, accounting for 47 of the 213 Government Major Projects Portfolio (GMPP) in 2024-25.
In December, the National Audit Office (NAO) published an overview of its performance and said progress on 12 of those projects was rated 'Red', meaning that their successful delivery "appears to be unachievable".
And the NAO added: "Over many years, the MoD has regularly experienced difficulties delivering many of its projects to required performance, cost and time".
In addition, the NAO report was critical of the MoD's administration, noting that for projects valued above £20 million it currently takes the MoD an average of six and a half years to award a contract.
The 2025 SDR recommended a new "segmented approach" to MoD defence procurement to deliver contracts within two years.
Challenges to come
Military analysts cite the rising threat from Russia since 2022, the current war in the Middle East and questions over the future of the US in Nato as powerful reasons for the UK to spend more on national defence.
General Sir Richard Barrons - one of the authors of the SDR in 2025 - told the BBC: "We've now entered a very new era in global affairs, with much greater risk but we're entering it with the armed forces we were left with for a much more comfortable, peaceful time."
A government spokesperson said: "We are delivering on the Strategic Defence Review to meet the threats we face."
"It is backed by the largest sustained increase in defence spending since the Cold War, with a total of over £270bn being invested across this Parliament."
Additional reporting by Gerry Georgieva
Correction: 15 April 2026: The original article used MoD annual figures from October 2025 to show there were 11 frigates. A subsequent Parliamentary answer reduced that figure to seven. We also sourced a figure of 137 Eurofighter Typhoons to a House of Commons Library briefing from November 2025. After consulting the MoD we have changed that number to 107.
