Theresa May has refused to commit publicly to Britain remaining a “tier one” military power amid fresh concerns from defence chiefs about Armed Forces budgets.
The Prime Minister became embroiled in a row with military top brass and the Defence Secretary Gavin Williamson after it emerged she had asked for a formal definition of what constitutes a “tier one” power during a discussion about the ongoing UK defence review.
It prompted fears that Mrs May is prepared to contemplate downgrading Britain’s military status after making the NHS her top spending priority.
Speaking in Downing Street after a meeting with the Nato General Secretary Jens Stoltenberg, Mrs May insisted Britain would remain a “leading defence nation”.
However she pointedly refused, when asked, to use the phrase “tier one” to describe Britain’s future status as a military power.
One well-placed source said her response would be read in defence circles as “a worrying admission that Britain’s military prowess could be under threat”.
The Ministry of Defence regards Britain, the US, Russia, China and France as the world’s “tier one” powers, as they possess a nuclear deterrent, special forces, intelligence-led counter-terrorism capabilities and the ability to fight land, air and sea wars around the world.
Defence sources said Mrs May had caused alarm among military chiefs after she asked General Sir Nick Carter, the Chief of the Defence Staff, to define what “tier one” military status meant during a meeting in Downing Street on Tuesday.
One highly-placed source told The Telegraph: “It caused surprise and a lot of concern because she has been Prime Minister for two years, in ultimate charge of our Armed Forces, and she has never before questioned what a tier one military power is.
“The fact that she has asked for a definition of it now is being interpreted as a sign of wanting to depart from that.”
Mrs May insisted that reports of her asking Mr Williamson to justify Britain’s tier one status were “not accurate”, while aides suggested she merely wanted to ensure that the definition was up to date and included cyber warfare capabilities.
Tuesday’s meeting, which was also attended by the Chancellor, Philip Hammond, had been convened to enable Mr Williamson to update the Prime Minister and Sir Nick on the progress of the defence review, which is expected to report back later in the summer.
A defence source said: “The Armed Forces already regard their role as including not just land, sea and air but also cyber and space.
“Does the Prime Minister not recognise why the UK is special compared to other nations?”
Mr Williamson has argued for months that Britain needs to increase defence spending as the MoD faces a funding shortfall of £20 billion over the next decade.
Mr Hammond has made it clear that the £20 billion a year boost to the NHS announced by Mrs May on Monday means there is no cash left for major budget increases for other departments.
The Telegraph understands that frantic work is being conducted in the MoD to finalise the details of the defence review, known as the Modernising Defence Programme (MDP).
It was originally hoped the review would report substantial conclusions at the Nato summit next month, but it appears now that any announcements will lack detail pending further work over the summer.
Mr Stoltenberg, visiting London ahead of a major Nato summit next month at which Donald Trump’s commitment to the organisation will be the major concern, said the UK was able to play a leading role in Nato because it has "full spectrum" defence capabilities and spends more than 2% of GDP on defence.
He said: “I expect the UK to continue and to maintain that role,” but warned that “to maintain that role, you need to spend and invest in defence...we need all the capabilities the UK provides.”