When a report from the World Health Organisation came out a few days ago, the media highlighted an extraordinary fact: that life expectancy in one deprived area of Glasgow is lower than in India, Philippines, Poland, Mexico and Cuba. This, you might think, is attributable to booze, fags, bad food and lack of exercise.

You would be right - but only partially so. The WHO report (Closing the Gap in a Generation) has a much bigger message, summed up in a single sentence: "Social injustice is killing people on a grand scale." That means what it says. Fat, sugar, cigarettes and alcohol are certainly killers, and a propensity to indulge in them is itself related to income and social status. But even if you eschew bad habits and lead a blameless life, your socio-economic status is likely to get you in the end. Inequality is the biggest killer of the lot.

The evidence was set out in The Status Syndrome, a book published in 2004 by Michael Marmot, the British professor who headed the commission that produced the WHO report. He quoted a study of office-based civil servants that first highlighted health's "social gradient" in the 1990s. It found that, at each grade down the Whitehall hierarchy, mortality increased. Between the ages of 40 and 64, those in the bottom grade were four times more likely to die than those at the top. Beyond retirement, the gap narrowed, but even in their seventies and eighties, men in the lower grade had twice the risk of death. As Marmot put it, "differences in lifestyle provide only a modest explanation". For example, smoking, cholesterol, blood pressure and so on explained only a third of the difference between the top and bottom grades in the risk of dying from coronary heart disease.

Without the right social policies, economic growth “brings no benefit to health”

I do not think we have yet grasped the import of this and similar research. We traditionally assume that health improvement is delivered by medical advances, better hospitals, more doctors and more spending on health services. Most political argument is about how to achieve these ends, with the role of preventative health - improved lifestyles - now adding a further dimension. The WHO report is saying something quite different: health is political in the broadest sense because it is influenced by the distribution of power, income, goods and services. Here are some more facts. US blacks are rich by world standards but, in a highly unequal country, most are very poor by local standards. People from Tunisia, Jamaica, Panama, Libya, Lebanon and Cuba all have higher life expectancies than the US black population. If black mortality rates were the same as those for US whites 886,202 deaths would have been averted between 1991 and 2000. Over the same period, 176,633 lives were saved by medical advances.

The WHO report shows that, if we want to achieve health equity and close the gap between rich and poor, we have to abandon the "Washington consensus" that has dominated western political and economic thinking for 25 years. Take the "flexible workforce" sought by new Labour as well as the Tories. Temporary, part-time and insecure work are all associated with poor health, according to the WHO report. Take the trend towards harsher social security schemes, means-tested and "targeted" at the "deserving" poor. The WHO insists that "generous universal social protection systems are associated with better population health".

Access to free education as well as free health services is important; the WHO deplores the user charges being imposed on many developing countries in the name of balancing state budgets. Progressive taxation, a strong public sector and private-sector regulation are all essential, the report argues. "Community or civil society action," it adds, ". . . cannot be separated from the responsibility of the state to guarantee a comprehensive set of rights and ensure the fair distribution of essential . . . goods . . . Top-down and bottom-up approaches are equally valid." Are you listening, David Cameron?

Above all, we should abandon the belief that everything must be sacrificed to economic growth. Without the right social policies, says the WHO report, growth "brings no benefit to health". Up to a certain, quite low level (which most of sub-Saharan Africa hasn't reached), higher national income brings dramatic health gains. Beyond that, the effect is slight and inconsistent.

The WHO report demands a revolution in current political thinking. The case for social justice, it shows, does not rest on ideology or class envy, but on "an ethical imperative", a preference for life over death.

It should be read, in full, by every politician on earth.