LONDON - The Army is losing the equivalent of one battalion a year as a result of illegal drug use, researchers said on Friday.

This was more than the number of fatalities and serious casualties in both Iraq and Afghanistan, the Medical Research Council Biostatistics Unit claimed.

Analysis of figures from the Ministry of Defence by the body, which was published in the Journal of the Royal United Services Institute, found there had been a four-fold increase in soldiers testing positive for cocaine.

It said that figures showed that positive tests for illegal substances in the Army rose from almost 520 in 2003, to 795 in 2005 but fell to 769 last year.

The unit said this was the equivalent of losing more than one battalion a year to drug use. The MOD rejected the research findings, saying that drug use in the army was not widespread.

Professor Sheila Bird, a unit senior scientist, labelled the findings as worrying and warned there could be more.

"What is worrying from our study... is the sharp increase in the proportion of soldiers testing positive for cocaine, a sharper increase than in 16-24 year olds in society at large," she said in a statement.

"The interim period coincides with major combats in both Afghanistan and Iraq and there is natural concern that the rise in cocaine use may be a direct result of increased combat stress. This could just be the tip of the iceberg."

But an MOD spokesman refuted the claims that drug use was rife despite admitting that more soldiers had tested positive.

He said positive detection over the past four years averaged 0.77 per cent compared to almost 10 per cent in other "civilian workplaces"

"Drug misuse is not widespread in the Armed Forces," he said. "Drug misuse is incompatible with service life and is not tolerated. The increase in individuals testing positive for cocaine is a reflection of society as a whole."

He said that the MOD has a compulsory drug testing police to "reinforce the message that drug use is unacceptable".