The ministry had since 1998 bought around 24,000 Provigil pills, a drug licensed in Britain only to remedy rare sleeping disorders, the Guardian newspaper reported.

According to figures from the Defence Medical Supplies Agency, which provides medicines to Britain's military forces, 4,000 of these tablets were delivered in 2002, shortly before troops entered Iraq.

If used by people with no medical need, Provigil could keep them awake for long periods of up to several days, the paper said.

Some other countries have previously used amphetamines to help troops stay alert and awake for long periods, but the drug is addictive and can make users aggressive and impetuous.

However the use of any stimulants by the British military remained controversial, the Guardian said.

WAR.WIRE