The Army's Chief of General Staff has warned that shortfalls in military resources caused by spending cuts "could become quite dangerous, quite quickly".
Speaking as the Ministry of Defence face a new round of savings as part of Government-wide reductions of £11.5bn to be outlined in the 2015/16 spending review, General Sir Peter Wall has warned that cuts would be "very disruptive".
The defence budget has some protection in Chancellor George Osborne's spending review, to be outlined on June 26. It will include a 1% increased in equipment budgets from 2015, but Defence Secretary Philip Hammond must still make a 5% overall reduction.
General Wall expressed concern at the prospect of these savings being made while the armed forces were still absorbing previous deep spending cuts.
In an interview on the Britain's Last War documentary aired on Sky News last night, presenter Jeff Randall asked him: "The forthcoming spending review seems sure to bring further cuts to the defence budget, and the arms budget, leaving a considerable gap between planned capabilities and available resources. How dangerous is that gap?"
He replied: "I think it could become quite dangerous, quite quickly."
He went on to say: "We have got to the point in a number of parts in our set up where we can't go any further without seriously damaging our professional competence and our chances of success in the battlefields of the future.
"It would be a brave claim to say an organisation can never make more efficiencies but we do need the time to let our new structures bed in, for those efficiencies to get delivered.
"Imposing more on us now, before the last round of efficiencies have really materialised properly in a balanced way, would be very disruptive."
Senior MoD sources say a deal with the Treasury that would not involve any further reduction in military numbers or capability was close. However, leading figures in the forces have echoed General Wall's concerns.
Speaking in the same documentary, Lieutenant General Nick Carter, the UK's most senior officer in Afghanistan, said that politicians should "look themselves in the mirror each morning" and ask if they felt the risks were manageable.
"At the end of the day our politicians need to determine what they want the Army to do. And if they determine that the Army's going to do less, then it's reasonable for them to reduce it still further," he said.
Labour have warned that the government are taking a "huge gamble".
Shadow defence minister Kevan Jones said: "The government have cut the Army without a replacement plan in place. The country will worry about strategic shrinkage by stealth."
An MoD spokeswoman said: "Like all Whitehall departments we are currently negotiating our financial settlement for the 2015-16 Spending Review.
"Although no final decisions have been taken we have been clear that we would first and foremost seek to find genuine efficiencies that would enable us protect front-line capabilities and protect military manpower numbers.
"Whilst this process is ongoing it would be inappropriate to comment further."