War casualties put UK hospitals under strain – ahead of fresh Afghan offensive

The demands are so great that the Ministry of Defence will today announce an increase in the number of ward beds at its rehabilitation centre, at Headley Court in Surrey, from 66 to 96, the Guardian has learned.

The report comes as ministers have warned of the prospect of further casualties as 4,000 British troops prepare to launch Operation Moshtarak – which means "together" in Pashtu – with US marines and Afghan forces. The aim of the operation, the biggest since the conflict in Afghanistan began, is designed to clear the town of Marjah in central Helmand, a Taliban stronghold and centre of the opium trade, of insurgents.

Bob Ainsworth, the defence secretary, has warned of a "very real risk" that British lives will be lost during the fighting.

The National Audit Office report details the growing strain that medical units are being put under by the ferocity of the fighting in Afghanistan.

Selly Oak hospital in Birmingham, where the MoD has a contract to treat seriously wounded troops, might have to displace civilians to make way for extra military patients, the report says.

The main field hospital in Afghanistan at Camp Bastion is coping with casualty levels, but operating close to capacity, it says. Contingency plans for providing further capacity back in Britain for injured troops have improved, but should be developed further, it adds.