Lonmin has announced it is planning to step up its drive to combat Aids, after a study showed a quarter of volunteers tested at the company's South Africa operations are HIV positive.

The firm, which is the third biggest platinum group metals producer in the world, says it will provide anti-retroviral drugs (ART) to all employees who need them.

Beginning on December 1st, World Aids Day, the company will target its 26,000 South African employees in a bid to tackle the issue.

Ed Haslam, Lonmin chief executive, told Mineweb that the costs involved presented a clear case for providing help.

'We have never before been in a position to look at [the problem of HIV/Aids] in such a scientific way. Now we know the scale of the problem, we can tell shareholders what the cost will be,' said Mr Haslam.

Lonmin estimates that HIV/Aids will add a maximum of US$6 per pgm ounce to its annual production costs by 2006, a total of nearly $12 million.

This figure has been substantiated by research conducted by the Actuarial Society - its financial model suggested that, at the peak, 26 per cent of Lonmin's employees would be HIV positive in 2006.

Lonmin said it was now considering extending the provision of ART treatment to employees' dependants, depending on the future actions of the South African government.