The commander of the country's biggest RAF station has insisted it is keeping up with the need for aircraft to support military operations in Iraq and Afghanistan.

Group Captain Malcolm Brecht conceded that there had been times when RAF Brize Norton, in west Oxfordshire, had "struggled to cope" with the demands of moving troops and equipment and providing in-flight refuelling of fighter jets.

But the base's ageing fleet of VC10 and TriStar planes was still up to the job, he said.

His comments followed publication on Thursday of a report by the House of Commons Defence Select Committee, which said there were "real doubts" that the former airliners - which are up to 40 years old - could stay in service until early in the next decade.

The committee said that it was "very concerned" that last November only 41 of the 75 Tri-Stars, VC-10s and Hercules transport planes - based at Lyneham in Wiltshire -were available for "required tasks".

Brize Norton is the home base for 16 VC10s and nine TriStars, both types capable of air-to-air refuelling as well as transporting men and equipment, and four large Boeing C-17 heavy transport planes.

Another C17 is on order, but the MPs said the RAF should urgently consider buying more.

Of the current fleet, two VC10s and one TriStar are permanently deployed to the Middle East for aircraft refuelling, while the other planes are operating on a daily basis to both Iraq and Afghanistan, as well as covering other military duties.

Gp Capt Brecht said: "There have been complaints about delays, but the evidence is that we are continuing to deliver.

"Nobody predicted the impact of 9/11 and the ageing platforms of our aircraft have caused some complications.

"We're deploying over great distances and have to keep the aircraft we have up-to-date and modified to operate in what are hostile areas in both Iraq and Afghanistan."

He added: "You have to remember we're supporting operations worldwide. As well as the two theatres in Iraq and Afghanistan, we have relief commitments elsewhere, and we have to rely on chartering civilian aircraft for some of that work.

"There's an expectation that in difficult circumstances everything will be delivered on time. We're running to capacity.

"But there are sometimes knock-on effects, for example getting troops back home on time, when we have unexpectedly to fit in repatriation or aero-medical flights."

Brize Norton is undergoing a £47m expansion programme and will be home to the next generation of RAF in-flight refuelling tankers and transport aircraft from 2012.

The refuelling fleet will be made up of converted Airbus A330 airliners, while new Airbus A400M transport aircraft will replace the oldest Hercules planes.