The drug is widely seen as the most promising treatment for combating any future pandemic of bird flu in humans.

The previously little-known Indian pharmaceutical firm Hetero Drugs has been granted the licence.

The decision could make it easier and cheaper for poorer nations to acquire stocks of the drug.

The Swiss drugs giant developed, and has patent protection for, a product that is in great demand from governments around the world.

They all want to build up stocks of Tamiflu - known generically as oseltamivir - to cope with the anticipated spread of bird flu to humans.

This appears to be only the second such manufacturing licence Roche has awarded.

The first one went to a Chinese firm, the Shanghai Pharmaceuticals Group.

It is a sign that Roche is responding to intense pressure from poor countries.

They have been worried that Roche on its own cannot make enough of the drug to meet demand - and that the prices it charges Western governments are too high for developing nations.

Roche meanwhile has claimed that most other drugs firms do not have the skills to make Tamiflu, a year-long process involving fermentation of e-coli bacteria.

The company says Hetero Drugs is among the first to demonstrate that it is technically capable of making a reliable generic version of Tamiflu.