Britain is buying 14.6 million courses of Roche’s antiviral drug Tamiflu to protect against a potential flu pandemic, the government said on Tuesday.

Countries around the world have been stockpiling the drug to combat a possible pandemic of bird flu, which has killed 47 people in Asia. The British order will provide 7.3 million doses by next April and the rest as soon as possible in 2006-7.

Assuming a pandemic does not begin in the near future, UK supplies should be enough to treat one in four of the population - the maximum number the WHO predicts might be infected in an outbreak.

Britain’s Chief Medical Officer Liam Donaldson told reporters existing flu vaccines would offer no protection against a pandemic strain, so Tamiflu would be used to treat people while a new vaccine was developed.

Steps had been taken to speed up flu vaccine production once a pandemic strain of flu emerged but he said it would still take four to six months to make a vaccine that matched the exact strain of the virus.

“Nothing will come early enough to save every life,” admitted Health Secretary John Reid. However flu pandemics usually came in waves, so hopefully there would be a vaccine in time for the second wave.

Without medical countermeasures, British experts estimate the number of deaths resulting from pandemic flu in the UK could be 50,000 or higher. Normal seasonal flu outbreaks result in around 12,000 deaths.

Professor Maria Zambon, head of the UK’s national influenza centre, warned of “formidable” technical difficulties in making vaccines against avian flu strains. However Britain was well placed as it had one of only two laboratories worldwide with the necessary containment facilities to produce candidate vaccines against such strains.

The Health Department released its latest influenza pandemic contingency plan, which calls for improved surveillance of bird flu in South East Asia - the most likely source of a pandemic strain of flu transmitted by people. The UK recently gave the World Health Organization 500,000 pounds (e730,000) to boost avian flu monitoring in the region and improve the chances of an early warning of a pandemic.

The 94-page plan also recommends preparations to reduce the risk of spread of the disease, including restricting travel, closing schools, and cancelling football matches or pop concerts and warns hospitals and industry to prepare for high rates of staff absenteeism.

“For planning purposes, the most likely scenario, based on previous pandemics, is a cumulative clinical attack rate of 25 percent of the population over one or more waves of around 12 weeks each, weeks or months apart. This compares with the usual seasonal influenza attack rate of 5-10 percent.”

Dr Anarfi Asamoa-Baah, assistant director general for communicable diseases at the World Health Organisation, said the plan showed that Britain was at the forefront of international pandemic preparations. “We hope that every country will develop their preparations to the same high degree.”