New statistics from the ONS have revealed that women in the most deprived areas of England can expect to have 19 fewer years of healthy life than those in the most advantaged areas. For men, the figure isn't much better, with a gap of over 18 years. To put that into perspective, those born in the poorest parts of England can now expect to live the same, or fewer, healthy years as someone born in war-torn Liberia, Ethiopia or Rwanda. And a third of people in England won't reach 60 in good health.

The temptation, as always, is to assume that those at the bottom eat poorly, do little exercise, drink a lot and take drugs. In short, it's their fault. But 94% of people on low incomes don't take drugs, and people in the richest fifth are actually twice as likely to drink heavily than those in the poorest fifth. Inconvenient as this may be to some, there isn't some inherent character flaw that only afflicts the poor.

As researchers around the world have demonstrated many times, it is the financial gap between rich and poor that is significant, not their lifestyles.

More unequal societies are more stressful ones, where people are encouraged not just to "get ahead" but to claw their way past others while pulling the ladder up behind them. Back in 2009 we demonstrated in The Spirit Level that people in more unequal societies suffer more violence, less social mobility and trust each other less. Greater emphasis is placed on the individual at the expense of the wider community, with collaboration and the building of meaningful relationships rejected in favour of the pursuit of status. Social stress is why those at the bottom, or those with "low status" suffer most. But is it also why the rest of us also do worse than our peers in more equal countries.

When The Spirit Level was published it was attacked by free-market fundamentalists who found the evidence to be at odds with their world view, in a similar way that evidence of anthropogenic climate change is attacked by "sceptics". But recently we have published a review of the extensive new research literature which shows strong evidence of causality. Inequality is not just vaguely linked to a range of health issues, it directly causes them.

The UK's extreme level of inequality, and the damage it does to our health and our society, is not accidental. In the late 20th century most developed countries experienced rising inequality, but in the UK this went further and faster than elsewhere. As a nation we made choices that exacerbated the situation, such as giving tax cuts to the richest at everyone else's expense. The UK adopted a culture of inequality, in which the rich are referred to in financial publications as "talent" or "wealth creators" but the rest of us are "labour costs" to be reduced rather than invested in. As if hard work and talent were confined to the super-rich, these terms are now used as a convenient excuse for pay far beyond the dreams of avarice. Work by the Equality Trust has even found that a FTSE 100 CEO is today paid on average 342 times that of a national minimum wage worker.

The inequality apologists and deniers can continue to bury their heads in the sand, but for the rest of us it is clear just how vital inequality reduction is for a healthier and happier society. The effects are lifelong. As we showed in a new study of child wellbeing, children in more equal societies do better on a wide range of measures, while as inequality increases, children suffer the consequences.

Political parties with the population's wellbeing at heart need to make a commitment to greater equality. This isn't just good public policy, it would also reflect the wishes of voters. Eight out of 10 people say the income gap is too large, and the subject of poverty and inequality is now, according to Ipsos MORI, one of the five most important issues for the electorate, higher than education and schools.

Committing to reduce inequality could be a matter of victory or defeat for politicians, and it could, literally, be a matter of life and death for the rest of us.