Delegates at a conference in London will debate today how to tackle HIV, after the United Nations called for more work to combat complacency over deaths from Aids-related illnesses.

UN envoy Stephen Lewis warned that the Aids pandemic is worsening, particularly in Africa where almost two and half million people have died this year.

He called on Prime Minister Tony Blair and US President George Bush to spearhead new efforts to tackle the situation, describing rising death rates in Africa as “mass murder by complacency”.

It is thought around 42 million people around the world have HIV or Aids and the condition claims 8,000 lives a day.

The HIV virus, which can lead to a sufferer contracting Aids, was discovered exactly two decades ago and there are currently no cures or vaccines.

Treatments have been developed to delay the onset of Aids, reduce the effect of the symptoms, and extending a patient’s life span.

Scientists have argued that reforms to social, legal and economic environments, especially in developing countries, are critical if attempts to prevent infection are to be successful.

Researchers at the University of California last week also called for a new promotion of “evidence-based” solutions.

They hope to popularise the ABC approach, in which A stands for Abstain, B for Be faithful and reduce partners and C for condom use.

It is also supported by Archbishop Desmond Tutu, President Museveni of Uganda, the World Bank and the Global Fund for Aids.

More than two-thirds of HIV cases in Britain are diagnosed in London, with a high prevalence of cases in Brighton and Manchester.