The Armed Forces would struggle to cope if the country was hit by a pandemic flu, with more than 50 per cent of military personnel laid low, an internal Ministry of Defence document indicates.

The Royal Navy, Army and RAF would be so badly hit in the “worst-case scenario” because of their close working environment, particularly on warships, that no military personnel would be available to help the civil authorities, the study says.

“The priority ... will be maintaining critical military operations with little or no spare resource to provide military assistance to the civil authorities,” says the internal MoD document, which is in the form of a guide for defence personnel.

In past crises, ranging from floods and foot-and-mouth disease to national strikes by firemen and petrol tanker drivers, the Armed Forces have played a key role in assisting the civil authorities.

However, with dire predictions of heavy flu casualties - up to 750,000 deaths and more than one million people needing hospital treatment - it is accepted officially that the Armed Forces would have to spend all their time ensuring that there were sufficient personnel to carry out basic military tasks and maintain operations abroad.

Experts have predicted the inevitabiity of another flu pandemic - there have been three global outbreaks in the past 100 years - and that it might come in several waves of three to six months over two years.

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