Nelson Mandela has called on European leaders to match a United States' financial pledge on action against HIV/Aids.
Millions of Africans are living with HIV/Aids
The veteran South African statesman told a conference on the disease in Paris that the number of people killed, especially in the developing world, represented a travesty of human rights.
President George W Bush has promised $15bn to fight the disease in Africa and the Caribbean.
About 5,000 scientists and doctors have gathered in the French capital for the biggest Aids convention this year - 20 years after scientists established the links between HIV and Aids.
Mr Mandela said the world had failed to translate improved scientific research into action in combating Aids.
42m people have HIV/Aids
5m became HIV+ in 2002
3.2m died from Aids in 2002
SOURCE: UNAIDS 2002
Professor Robert Gallo, one of the scientists who first published evidence that HIV causes Aids, has denied that researchers have lost interest in seeking a vaccine because the focus of the crisis has moved to the developing world over the past two decades.
The US scientist told a BBC News Interactive forum that some neighbourhoods in his own city, Baltimore, had rates of HIV/Aids comparable to those of Africa.
Professor Gallo went on to stress that a lack of infrastructure in the developing world was hindering work to treat sufferers with vaccines.
"If the infrastructure is not there, we are going to create multi-drug-resistant mutants," he said.
The convention, which opened on Sunday and continues to Wednesday, was disrupted after Mr Mandela's speech by a dozen protesters demanding bigger funds to tackle HIV/Aids worldwide.
Mr Mandela smiled during the noisy but peaceful protest, clapping in time to the chant from the podium.
Delegates heard horrifying statistics on the continuing inroads being made by the disease with one speaker reporting that 90,000 people in Burundi alone needed anti-retroviral drugs - and only 1,000 were getting them.
But there was better news from Brazil where an aggressive safe sex campaign appears to have paid off.
Former President Fernando Henrique Cardoso rounded on the US for basing its Aids prevention programmes on sexual abstinence rather than condom use.
He urged the global community to learn from Brazil's example of setting up education campaigns, expanding basic health care and providing anti-retroviral drugs to all infected people.
Brazil has cut the death rate from Aids by 50% and hospitalisations by 75%, he told the conference.
"The Brazilian experience confirms that ambiguous and inconsistent messages like those [which] advocate abstinence and fidelity as solutions run the risk of generating a misleading sense of security," he said.
The conference opened in France, BBC science correspondent Richard Black reports, because it was French researchers who published early evidence that HIV causes Aids.
Professor Gallo, of the rival American team, told the BBC on Monday that a dispute with the French over who exactly had proved the link had been resolved 15 years previously.
"We absolutely have no disagreement on the history," said Professor Gallo, who is sharing the conference platform with the leader of the French team, Luc Montagnier.
"We call it co-discovery."
Despite 20 years of research, our correspondent notes, there is still no effective vaccine against Aids.
But with the modern science of genomics allowing researchers unprecedented insights into the workings of cells and viruses, a raft of potential new approaches to vaccination will be unveiled here.