Six joint NHS/ military hospitals in England, employing at least 1,000 regular army members, could be affected.

The six employ members of the army, navy and air force who work as NHS staff.

But they can be called up for exercises or conflict at any time.

The hospitals are:

• Derriford Park, Plymouth
• Frimley Park, Surrey
• Peterborough Hospital
• Queen Alexandra Hospital, Portsmouth
• South Tees, (formerly Northallerton), Middlesborough
• University Hospital Birmingham (formerly Queen Elizabeth's)

Spare capacity

A meeting of the hospitals' chief executives was held at the Department of Health in London on Thursday to help them plan for the loss of staff.

Any call-up could create a significant hole in each hospital's staffing, though it is unlikely all medical regulars would be deployed at once.

Inevitably in a state of war there are serious consequences not only for those involved in the war but also for those at home British Medical Association spokesman

For example, Frimley Park hospital has 241 army personnel working as doctors, nurses and healthcare assistants, out of a total staff of 5,000.

South Tees has 180 army personnel working there.

Peterborough Hospital, which has close links with the navy, has 200 military personnel working there, including 10 consultants, out of a staff of 3,000.

They will be advised to book cover for absent staff, and talk to neighbouring hospitals to see if there is spare capacity they can make use of.

Peterborough Hospital has in the past used local GPs in A&E and asked recently retired consultants to work for short periods.

Shortage

A spokesman for the Department of Health told BBC News Online: "In normal peacetime, there would be these meetings.

"But everyone sees the situation on the horizon."

A spokesman for the Department of Health told BBC News Online: "In normal peacetime, there would be these meetings.

"But everyone sees the situation on the horizon."

Dr Christopher Parnell, a consultant anaesthetist and a member of the reserves, (people who formerly served in the forces), said a large call-up would affect on the NHS.

He told the BBC: "The impact on the NHS's performance is difficult to quantify, because we don't know how many surgeons, how many anaesthetists, indeed how many NHS personnel will be involved."

Dr Parnell said some areas could find it difficult to find staff to stand in for those who are deployed.

"Anaesthetists, for example, are in short supply; in the NHS, in the services and in the reserve forces as well."

A spokesman for the British Medical Association said: "Inevitably in a state of war there are serious consequences not only for those involved in the war but also for those at home.

"This is compounded by the shortage of doctors both in the Armed Forces and in the NHS.

"Our troops abroad need our full medical support and this will have an effect on non-urgent care for NHS patients at home."