South Africa's constitutional court has ordered the government to provide a key anti-Aids drug at all public hospitals.

The drug helps prevent mother-to-child transmission of HIV-Aids.

Government is ordered without delay to remove the restrictions that prevent nevirapine from being made available

Constitutional Court of South Africa

The ruling is a major defeat for the government, which appealed in May against a similar decision by a lower court.

Meanwhile, a study in Uganda has shown that the latest anti-retroviral drugs can be used effectively in developing countries.

Patients were asked to buy drugs at subsidised prices and were monitored in a scheme run by the United Nations Aids agency and the Ugandan health ministry.

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Out of almost 400 patients who started treatment, 63% were still alive and continuing therapy after six months and 49% were still being treated after a year.

Poor food

One in nine South Africans is infected with HIV and between 70,000 and 100,000 babies are born HIV-positive annually.

"Government is ordered without delay to remove the restrictions that prevent nevirapine from being made available for the purpose of reducing the risk of mother-to-child transmission of HIV at public hospitals and clinics that are not research and training sites," the constitutional court said.

Drugs could stop HIV transmission to babies

The health ministry had originally argued that the drug was too costly and its effects unproven but changed its stance following the lower court's decision in May.

The government has made the drug available at "pilot-sites" and said this would be expanded later this year.

Thabo Mbeki's government has been widely criticised by Aids activists for restricting the supply of anti-retroviral drugs.

He has also questioned the link between HIV and Aids, stressing the role of poor quality food and housing in reducing the immunity systems of many South Africans.

Health campaigners believe that at least 30,000 babies could be saved from contracting HIV annually through provision of nevirapine.

Groups such as Treatment Action Campaign brought the court cases against the government, arguing that it was acting unconstitutionally by failing to provide drugs that would reduce transmission of HIV from mothers to their children.

They want immediate provision of the drug and Friday's court ruling is a major advance in their campaign.