Delivering the first Diana, Princess of Wales Memorial Lecture in London, Mr Annan urged world governments to follow her lead.

Diana helped higlight the plight of those living with Aids

"Were (Diana) with us today, I would say this - you won the hearts of millions by acknowledging you own human vulnerability, and you were among the first in the country to fight the conspiracy of silence and prejudice against Aids."

During the lecture at the Bank of England, Mr Annan said the moment when Diana was pictured holding hands with victims of the virus signalled a watershed in attitudes.

Martin Dawes in Lake Victoria, Kenya: The adult population is withering

He said: "Perhaps it takes a special kind of sensitivity to do what Diana did. The rest of us can only draw inspiration from it.

"Faced with her example, we simply cannot leave the neediest on this earth to needless death and degradation.

"She gave too much, and cared too deeply, for us not to honour her memory with action."

Mr Annan used the lecture, sponsored by the National Aids Trust, to highlight massive problems with Aids in the Third World, despite advances in treatment in the West.

Economies devastated

He said: "Every minute that passes, as you and I go about the routine business of our lives, four or more young Africans are infected.

"And every day, Africa buries 5,500 of its sons and daughters who have died of Aids."

He said that the scale of the disease was not just a tragedy for individual families, but was devastating the economies of some of the world's poorest countries.

He said: "It is taking away both breadwinners and those who look after the young, the old and the infirm. It is destroying the very fabric of society."

He said new HIV infections in east Asia and the Pacific rose by 70% between 1996 and 1998, with India now having more people living with Aids than any other country.

Low-cost treatment

"It seems an unending downward spiral of death and despair," he said.

Mr Annan called on governments to produce low-cost Aids treatments instead of just the costly procedure now available.

He said: "We must find low-cost, effective therapies that developing countries can afford."

The annual lecture is supported by the Diana, Princess of Wales, Memorial Fund, set up after her death in a car crash in Paris in 1997.