the prime minister had 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”.

Sir Keir of failing to properly fund the nation's defence investment plan during a “dangerous time”.

I never expected to write this letter, but I am forced to make decisions that would reduce the readiness of our forces and increase the risk to personnel on operations, and could make our country less safe.

the nation needs to defend the country at this time of rising threats

falls well short of what is required

Your DIP financial settlement - which I was first given in full on Monday afternoon this week - falls well short of what is required for defence and the country at this dangerous time.

I am now left with no other option than to submit my resignation as your Defence Secretary.

You spelled out the threats last week: 'it is our intelligence assessment, and the assessment of other countries in NATO, that there could be an attack by Russia on NATO as soon as 2030.'

Since then, 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.

The excellent and extensive cross-government work that completed in January – overseen by you, me and the Chancellor – confirmed the scale of the challenge and the rising demands on defence.

the government's defence investment plan falls "well short of what is required at this dangerous time"

John Healey quitting will send shockwaves shuddering through our military