Global warming and climate change pose ever more urgently the question of how the world shares its resources. Environmental constraints mean the old capitalist trick of making and promising an ever increasing cake will not work any more, or not for much longer anyway.

The question of how the cake is shared has to be addressed in order to avoid a century of (possibly terminal) conflict over resources with nations scrambling to maintain their fossil-fuel and growth-addicted economies. The task of progressives – and let’s be clear here, it’s a task in which we are currently failing – is to come up with a truly popular, democratic and enduring form of politics which will persuade the world to turn away from conflict and an unsustainable future.

I would suggest that reclaiming and proclaiming equality as the core of progressive politics is the way forward. In other words we must concentrate, above all, on massively reducing the gap between rich and poor and persuading people that it has to be done.

New evidence published by Wilkinson & Pickett in their book, The Spirit Level: why equality is better for everyone demonstrates that more equal countries in the developed world – those with a narrower gap between rich and poor – have markedly fewer health and social problems and are already more sustainable. Already their flatter and less competitive social hierarchies dampen the demand for conspicuous and excessive consumption and encourage a shorter working-hours culture. Recycling rates are higher in more equal countries and their business leaders are more likely to support international environmental treaties. These countries also give more in overseas aid to developing countries which are, of course, the ones most immediately threatened by climate change.

Crucially, greater equality is also conducive to further moves towards sustainability. Countries that are more equal have higher levels of trust and it is this bedrock of trust which will be needed if we are to make real progress towards sustainable economic models. At present, the zero-sum seems to rule political discourse in too many countries. Too many people are distrustful and feel they can only win if someone else loses and they are unwilling to contemplate any changes to their lifestyle as they think others will not do the same. This destructive mindset can be changed by moves to greater equality, both in terms of fostering more co-operative and community-minded attitudes and also by maintaining high levels of well-being such that the transition to sustainability does not seem so difficult or unrealistic.

As well as focusing on equality as our core value progressives must also set out new, popular and transformative ways to achieve that greater equality. There is no great appetite in Europe for revolution – yet another classic and deep capitalist crisis has failed to raise up Marx’s grave-diggers in any significant numbers.

Also, despite a few signs of a political shuffling to the left, there seems little demand in Europe for more progressive taxes and greater welfare spending – or direct state intervention in the economy, with the possible exception of the financial sector.

Transformative routes to equality in the twenty-first century will therefore need to be innovative and be capable of seizing the popular imagination if they are to be adopted. A wholesale embracing of co-operative economics and related campaigns for pay justice – narrowing the ratios between high and low pay within all sectors of the economy – are two concrete proposals on the way to narrow the gap between rich and poor that seem to be gaining ground. These would go a long way to entrenching greater equality in the very structures of the economy and would be much harder for non-progressive governments to reverse in the future. We should now pursue these ideas vigorously.

Thanks to The Spirit Level we now have an enormous amount of hard evidence, both social and environmental, to buttress the traditional intuitions and arguments in favour of equality. It is time we deployed that evidence in order to deliver the popular majorities required to move towards societies that are not only good but also sustainable.

Watch Richard Wilkinson and Kate Pickett set out the main arguments of their book The Spirit Level