Birmingham’s Selly Oak Hospital will need to send increasing numbers of civilian patients to other parts of the country as it struggles to cope with the demands of treating soldiers injured in Afghanistan, a watchdog has warned.

The hospital, which treats British soldiers evacuated from conflicts overseas, is under “increasing pressure” due to the number of serious injuries suffered by members of the armed forces, said the National Audit Office, the official watchdog of public finances.

It was praised for the high quality of care it offers to patients - following a series of newspaper reports early in the Afghan and Iraq wars which claimed that service personnel were unhappy with the treatment they received.

The National Audit Office said: “Military commanders and the patients to whom we spoke have confidence in the clinical treatment.”

But the report, published today, also confirmed reports that soldiers were unhappy being treated on the same wards as civilians.

It said: “ Departmental surveys show patients are satisfied with being treated by civilian and military staff but they have concerns about being accommodated with civilian patients because the circumstances of their hospitalisation are so different.”

It will be easier to give military patients their own ward when a new state-of-the-art hospital, replacing Selly Oak Hospital and Queen Elizabeth Hospital in Edgbaston, is opened later this year, the report said.

A total of 522 personnel had been seriously injured on operations in Iraq and Afghanistan between October 2001 and the end of October 2009, and most of these were treated at Selly Oak before moving to a rehabilitation facility at Headley Court in Surrey.

Selly Oak also treats patients with minor injuries or who fall ill while on duty, and 1,425 patients have received treatment at Selly Oak or the Surrey rehabilitation centre since October 2007 alone.

The report warns: “Casualty numbers from military operations are placing increasing demands on Selly Oak and Headley Court but have been managed to date by taking measures to increase capacity for these patients.

“To manage increased levels of military casualties, some civilian care at Selly Oak has been outsourced to private providers and other NHS facilities.”

So far, Selly Oak has moved 200 civilian patients to different hospitals to allow it to cope with military casualties, the report said.

It added: “Any significant rise in military patients is likely to displace further the treatment of civilian patients at Selly Oak.”

And rates of minor illness and inury among soldiers is increasing rapidly, the report said, although there was no clear reason why.

It warned: “The rate of minor injury and illness has almost doubled in three years.”

Amyas Morse, head of the National Audit Office, said: “The good news is that my report has found that treatment for seriously injured personnel is highly effective.

“Alongside this positive finding, we point out the need to continue to improve contingency planning for facilities in the UK in the context of a longer term conflict, and the importance of increased efforts to prevent disruption due to rising levels of short term illness.”