Millions of children's lives are being lost or blighted because pledges to take action to curb the spread of malaria have not been kept, either by heads of state in poor countries or by wealthy donor states, a leading economist says. Jeffrey Sachs, special adviser to the UN secretary general, Kofi Annan, launched a hard-hitting attack on leaders in both the affluent north and the poor south on the eve of a UN general assembly session on malaria which will assess progress since the pledges two years ago at an African summit on malaria.