A senior RAF source warned that delaying or scrapping the F-35A would leave Britain vulnerable and unable to counter Russia should Moscow threaten the UK with low-yield nuclear weapons.
“We have got to walk the walk of the talk we talk. The Government has to match word, thought and deed. Anything they do or do not do will be picked apart by Moscow,” they added.
“From all the options that Russia has in conventional means… we very quickly run out of options for response. The F-35A helps us address this.”
Meanwhile, Sir Richard Shireff, a former NATO deputy supreme allied commander, said Britain would “pay in blood” if it fails to boost defence spending.
He told the Daily Mail: “It has been over a year since the Government concluded its review of our Armed Forces. The investment plan should have been published last autumn.
“The military is tearing its hair out waiting for Keir Starmer to make a decision. British jobs are on the line. Our national security is being undermined.”
The funding row has reportedly led to a clash between John Healey, the Defence Secretary, and Rachel Reeves, the Chancellor, forcing the Prime Minister to step in.
The MoD is facing a £28bn funding shortfall in the next four years. However, the Chancellor has been resistant to providing the investment to cover this, and it is understood a figure closer to £18bn has been agreed.
The Telegraph understands other government departments have had their budgets reduced to make up some of the shortfall, further inflaming tensions.
Heidi Alexander, the Transport Secretary, is understood to have pushed back against demands for bigger cuts in her capital budget to fund Sir Keir’s military investment plan.
Sources suggested any cuts would not be “that much more beyond” the 1 per cent being demanded across all Whitehall departments, but would have been higher had Ms Alexander “not beaten them down”.
It is understood that no major transport projects will be downgraded or axed because of their importance to economic growth, although there will be delays to some schemes.