Fresh doubts over the armed forces' ability to cope with protracted conflicts are raised today in a report exposing "critical gaps" in air operations.
The Whitehall spending watchdog raised the alarm over delays in delivering new aircraft which it blamed for problems in the RAF's ability to carry out crucial tasks.
It said the effect was already being noticed in Afghanistan ahead of the withdrawal of British troops by the end of the next year.
The National Audit Office (NAO) disclosed that the Ministry of Defence had already spent £787m trying to plug the gaps caused by the delays to the Future Strategic Tanker Aircraft (FSTA) and A400M transport aircraft programmes.
It said officials were considering extending the life of its elderly VC10s, which were supposed to be taken out of service in March, in an effort to eke out as much refuelling capacity as possible.
Once they have been grounded, the RAF will be forced to rely on another ageing aircraft – the Tristar, which goes out of service next year – to meet its air-to-air refuelling requirement until the replacement FSTA is ready to take over.
Although the first of the planned 14 FSTAs has now entered service, fuel leaks and fuelling basket "instability" have meant it has had to be restricted to transport duties until the technical problems have been resolved. Overall, the NAO said there would be some "critical gaps" in air-to-air refuelling and tactical air transport until 2017, and a one-third shortfall in the MoD's stated requirement for tactical air transport aircraft after 2022.
"The delays in introducing the new aircraft and budgetary constraints have caused critical shortfalls in some capability areas," the NAO warned.
"This is particularly apparent up to the end of UK combat operations in Afghanistan in 2014, when both air transport and refuelling aircraft will be extremely busy, but also from 2022 for air transport, when the Hercules C130J aircraft goes out of service early."
In its annual report on the MoD's major equipment projects, the NAO also disclosed that delays to the £32 million Falcon communications system, which was developed for use in Afghanistan, meant it would not now be ready until after British troops have withdrawn in 2014.