The UN Children's Fund (Unicef) estimates that by the turn of the millennium there will be ten million sub-Saharan African children orphaned due to Aids.

The high number of orphans is placing a burden on fragile societies

Deputy Director Stephen Lewis launched a fierce attack on Western governments for spending £40bn on the Kosovo conflict, but only 1% of that on fighting Aids in Africa.

"People talk about a Marshall Plan for the Balkans," said Mr Lewis. "What about one for Africa?"

In some countries, the number of children under the age of 15 whose mother, or even both parents have died from Aids is approaching one in ten.

Uganda suffering the most

In Uganda, at the end of 1997, 1,100 children out of 10,000 were in this horrifying situation.

Unicef says that the disease has cancelled out many of the economic progress made by third world countries in recent decades, calling it the "biggest crisis"Africa has ever faced.

Many African countries run extensive Aids education programmes

And it predicts that the situation will be far worse by the turn of the century.

A 50-year social programme will be needed to repair the damage caused by the devastation of a whole age group, it says.

The worst 24 countries in the Aids orphan league table, according to the 1997 figures, all lie in sub-Saharan Africa, and Unicef claims that the number of orphans has probably grown by more than 50% since then.

Orphan explosion in Asia expected

The number of Aids orphans in East and South Asia, although currently lower, was expected to grow by well over 150% in the same period.

Anita Tiessen, a Unicef spokeswoman, told the BBC that things were going to get worse before they started to improve.

"Lack of information is not the problem any more - the main problem now is low to encourage social change and help people not to contract Aids."

The organisation is promoting action in a number of areas, including trying to discourage polygamy, as this helps spread the disease.

The rise of drug use in Eastern Europe has spread HIV

Unicef is also hoping that negotiations with major pharmaceutical companies will bring down the price of anti-HIV medication, which at present is prohibitively expensive.

It is also working to greatly reduce the transmission of the disease from mother to infant by giving the correct drugs before birth to the pregnant woman.

But lack of funding is hampering its efforts, and Ms Tiessen said the problem could become worse as societies struggled to compensate for the loss of some of its most productive members.

She said: "When HIV and Aids became manageable diseases in the West it dropped off the political agenda - we have to get it back on again."

Drugs and unsafe sex in Eastern Europe

The Unicef report also contained worrying news of the increase in HIV infection amongst adolescents in Eastern Europe.

Figures show that, in the Ukraine, there are 18,000 15 to 19-year-olds are infected, an increase put down to rising intravenous drug use and low awareness of safe sex.

Spain is currently the worst country in Western Europe for HIV infection among teenagers, with 5,400 15 to19-year-olds living with the virus. The UK has about 600.