Kim Sengupta: In these tough economic times, it's clear that the defence budget will have to be cut

All three services are scrambling for scarce resources - the RAF is particularly vulnerable

It was a startling admission to make. The Chief of Defence Staff, Air Chief Marshal Sir Jock Stirrup, said it was "certainly plausible" that the RAF – which he was head of until 2006 – may cease to exist. Within minutes his admission was headline news on television, a graphic illustration of the massive cutbacks being faced by the British military.

There was a misunderstanding. Sir Jock had, in fact, said it was "certainly plausible" that the services would escape merger. However, this in itself was hardly a declaration of confidence, and he went on to say: "There are interesting issues to be debated here... There is an issue of organisation and the way you do that."

All three services are scrambling for their cut of scarce resources in the knowledge that the main political parties are clear that the defence budget will need to be slashed in the current straitened economic times.

The RAF is particularly vulnerable. Some defence officials are asking why its role cannot be subsumed into the Army's Air Corps and the Navy's Fleet Air Arm. Critics charge that the service is stuck in a Cold War mentality with £18bn spent on the Eurofighter Typhoon and more billions on the F35 Joint Strike Fighter. More resources, they say, should have been spent on assets for a counter-insurgency operation such as Afghanistan – unmanned aircraft (UAVs), transport planes and helicopters which could be run by the other two services.

The RAF insists that it has already made significant economies and points out that, according to accepted doctrine, without command of air in Afghanistan by Nato, 10 times as many troops would be needed on the ground. The Royal Navy, too, had been predicted to suffer in the Strategic Defence Review (SDR) with one or both of the new aircraft carriers being jettisoned. Admiral Sir Mark Stanhope, the First Sea Lord, had made two speeches titled "Beyond Afghanistan" with an air of almost desperation, arguing that defence policy should not become too "Afghancentric" – in other words, focus on land warfare.

But, to general surprise, the Government appeared to be seeking to ring-fence the carriers from SDR cuts. There is a belief that this was not based entirely on military considerations but to preserve shipbuilding jobs during the recession.

The Army, some of whose senior officers have argued vehemently in private against the new aircraft carriers, say that beyond Afghanistan lie more Afghanistans; similar wars where "boots on the ground" and winning over the local population would be essential rather than expensive warplanes and warships which are relics of the Cold War.

The troops on the ground in such conflicts are particularly vulnerable to roadside bombs and mines – around 91 per cent of British and allied casualties in Afghanistan are caused by IEDs (improvised explosive devices). Millions have been spent on a tranche of armoured vehicles for Helmand under Urgent Operational Requirements, but many of them have continued to be vulnerable to blasts.

The Army has felt short-changed in recent defence budgets, despite doing the bulk of the fighting in Afghanistan and Iraq. The service's main aim is to avoid cuts in the number of troops and ensure more investment in equipment to combat IEDs. A failure by the SDR to deliver this would lead to a fierce reaction.