Truss government would need to boost military by 40,000+ and £157bn, analysis suggests

It is predicted that a Liz Truss government would have to grow the UK Armed Forces by more than 40,000 personnel and spend £157bn more to meet its commitment to increase defence spending to 3% of GDP by 2030.

The Conservative leadership candidate's pledge to boost defence spending from current levels of around 2% would be the most significant increase since the early 1950s, the Royal United Services Institute (RUSI) said.

Author of the report, Professor Malcolm Chalmers, explained: "To spend 3% effectively, the defence budget will require a significant increase in the size of the frontline – numbers of formations and platforms.

"An increase in service personnel numbers of 25–30% is likely to be needed to support an overall 60% increase of defence spending.

"This would increase total numbers of regular personnel from 148,000 today to around 190,000 in 2030, returning to the level last seen in 2010."

The Deputy Director-General of the defence and security think tank RUSI, said the next Spending Review, likely to be in November, will be the first sign of whether the new government is serious about a target of 3%.

Pathfinder troops from the British Army train for overt scenarios in Norfolk at night (Picture: Corporal Houghton/British Army).
Pathfinder troops from the British Army train for overt scenarios in Norfolk at night (Picture: Corporal Houghton/British Army).

If not, Prof Chalmers said, the new Prime Minister would need to act swiftly to reverse what would otherwise be a reduction in defence spending over the next two years due to soaring inflation, and outlined a number of military projects which are not currently fully funded.

"Items such as the new generation of fighter aircraft… which will replace our Typhoon jets, that's a big item," he said.

"The replacement nuclear warhead, which is still at an early stage but will involve a lot of money by the end of the decade – that's not fully funded.

"And the plans for a new generation of attack submarines which we could well be developing jointly with Australia, that again is not fully funded and many people, including Ben Wallace (Defence Secretary)… got a lot of indication that the Government would like to have more of those submarines because they're so valuable."

He added there is a lot of ambition to modernise the British Army "to be better prepared for what we’ve seen in Ukraine today".

"That requires extra investment in people as well as in kit," he said.

Watch: 'We will have to spend more' on defence, PM says.

"You don't want to be under-armed if you're facing a capable opponent like Russia.

"Clearly, the Ukraine war has created circumstances in which there's a lot more focus – political focus, public focus –  on defence."

Prof Chalmers added that the report outlines the ambition to increase service personnel by 25-30% by 2030, however, to do so, "you are going to have to start recruiting those people" and think about their housing and training and paying personnel in the Armed Forces more to attract them into the military.

He also said any considerations of increased defence spending would have to be weighed up against wider fiscal priorities such as the NHS.  

Prof Chalmers predicts any pace of spending growth would be "slower in the early years, before accelerating towards 2030", due to "capacity constraints" before greater infrastructure can be built to handle a larger military.

"This could mean that defence spending rises from 2.2% of GDP in 2022/23 to 2.5% in 2026/27, before increasing to a full 3% over the following four years."

The new PM, either Liz Truss or Rishi Sunak, is to be revealed on 5 September.