Water and sanitation are among the most powerful preventive medicines available to reduce infectious disease. The presence of a flush lavatory in a house, the UN report says, reduces the risk of infant death by more than 30 per cent. Sewers save more lives than antibiotics. Astonishingly, then - despite one of the Millennium Development Goals being to halve the number of people without water and sanitation - the amount of aid to this sector has, according to the Commission for Africa, fallen by 25 per cent over the past decade.

The problem is twofold. The first is that such basics are unfashionable among Western donor governments. The second is that many African and Asian governments do not prioritise the area; in Ethiopia the military budget is 10 times the water and sanitation budget; Pakistan spends 47 times more on guns than on sewers and clean water.

Why? Because water and sanitation are problems which disproportionately affect the poorest, women and children in particular, - a class which has no political leverage with urban Third World elites.

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The UN report is full of examples of strategies that have worked, and those that have not. It cites success stories in Thailand, Sri Lanka and Vietnam and comparative good news in South Africa, where water was once a symbol of apartheid division, but a system of entitlement has been introduced. It should be extended across the world, the report says, with all governments legislating for water as a human right, with a basic minimum of 20 litres per person per day - less than half of what we in Britain each flush daily down the lavatory.

To do that, the report says, would increase aid spending by about $4bn a year. That is less than Europe spends on bottled mineral water.