"DOWN THE DRAIN"

Heneghan's team say their analysis is the first based on full data - from 20 trials of Tamiflu, known generically as oseltamivir, and 26 trials of Relenza, also known as zanamivir.

At a briefing in London about their findings, Heneghan said the money spent on stockpiles "has been thrown down the drain" because, until now, the full data had not been seen by regulators, governments, doctors or patients.

"The original evidence presented to government agencies around the world was incomplete," said Fiona Godlee, editor of the British Medical Journal which has spearheaded a four-year campaign to force Roche to reveal all its Tamiflu data.

"And when they (the Cochrane review team) eventually received the full information on these drugs, the complete evidence gives a very much less positive picture."

But the European Medicines Agency (EMA) - which approved the drug for sale in Europe - disputed the claim they had not seen all the Tamiflu data.

Enrica Alteri, head of medicines evaluation, said EMA had seen and reviewed all 20 studies referred to in the review, and this new analysis did not raise any fresh concerns or alter the agency's assessment that Tamiflu's benefits outweigh its risks.

Wendy Barclay, a flu expert at Imperial College London with no links to the Cochrane Review or the drugs, said she still felt the benefits were worthwhile, particularly in a pandemic.

"If another pandemic came tomorrow, and the government had no drug with which to treat thousands of influenza infected patients, I imagine there would be a public outcry," she said.

The Cochrane review found that compared with a placebo, or dummy pill, Tamiflu led to a quicker alleviation of flu-like symptoms of around half a day (down from 7 days to 6.3 days) in adults, but the effect in children was more uncertain.

There was no evidence of a reduction in hospitalisations or in flu complications like pneumonia, bronchitis, sinusitis or ear infections in either adults or children, Heneghan's team said, and Tamiflu also increased the risk of nausea and vomiting in adults by around 4 percent and in children by 5 percent.

Godlee described the battle with Roche as a "really lengthy cat and mouse, Alice in Wonderland, bizarre experience of trying to get data on a drug which governments around the world were busy buying, stockpiling and spending billions of dollars on".

"Why did no-one else demand this level of scrutiny before spending such huge sums on one drug?" she said. "The whole story gives an extraordinary picture of the entrenched flaws in the current system of drug regulation and drug evaluation."