Next week, world leaders will meet in Rio de Janeiro to discuss how the global economy can tackle the joint challenges of global poverty reduction, social equity and environmental sustainability. The United Nations Conference on Sustainable Development  marks the 20th anniversary of the 1992 Earth Summit : hence the popular short-hand, "Rio+20".
For environmentalists, Rio+20 is one of the most significant events to happen for a generation. But that's precisely the problem. As long as it remains the preoccupation of the green movement, Rio+20 will deliver only a fragile consensus that will ultimately fail.
The natural environment is fundamental to supporting and supplying the basis of economic value. Yet we do not consider the protection and enhancement of the natural environment is a strategic economic priority. Part of the reason for this is because our conventional model of economic growth values short-term return and wealth creation, rather than long-term productive wealth. While we may increase GDP in the short term, our conventional approach to economic growth can actually reduce a nation’s wealth.
Ed Miliband recognised these limitations in a speech  to the Social Market Foundation last year where he told the audience that rules that encourage wealth creation focus on "short-term returns not the productive creation of long-term value". A major consequence is that resource consumption and the loss of ecosystems are treated as a benefit rather than a cost. And communities, co-operation and equality are undervalued in favour of creating conditions to maximise consumption.
An important challenge for Labour is now to translate Ed Miliband's vision for a "new economy" into a shared understanding of exactly what we want, and need, from the economy - and to be clear about the measures that will ensure that this can be achieved sustainably.
For many years there has been a lively debate about how the transition to a "green economy" will happen. However, no one has successfully managed to align the green economy with the everyday priorities of people, business and politics. Nor has anyone managed to set a pro-growth agenda that is also clear about the long-term productive value of a sustainable economy.
Most would agree that our expectations for the economy include job creation; competitiveness; the fair distribution of resources and wealth; fair and affordable access to food, water and energy; and enhanced biodiversity and ecosystem services. While these outcomes are complementary, much of the debate about our economic future has hitherto traded one aspect against another: green groups have one priority, business another, politicians another still.
Rio+20 provides a valuable political focus to continue work already underway on how Labour can address this. A question that the party might seek to answer is how we embed the three pillars of sustainable development - economic, social and environmental - into policy-making so that they become a natural by-product of the economy's total activities.
This would create huge economic opportunities for the UK - new green technologies, sustainable innovation, sustainability skills and sustainable investment products - all of which will also be instrumental in assisting emerging economies with the transition to a green economy.
The Labour Party has a strong track record on the green economy. The world’s first Climate Change Act  and the Climate Change Committee ; the 2005 Sustainable Development Strategy  with its recognition of the concept of environmental limits; the Sustainable Development Commission ; the Commission on Environmental Markets and Economic Performance  and the Low Carbon Industrial Strategy  are all good examples of the Labour government's successes.
The party's approach in government was based on an understanding that policy and regulatory intervention is necessary to correct the market failure of un-priced environmental costs and benefits - thereby reconciling the free market economy with environmental sustainability. It understood that a strong and robust economic-environmental policy framework would also encourage finance and investment in low-carbon, resource-efficient business operations and supply chains.
Green conservatism of the sought advocated by David Cameron is flawed in this respect as it fails to reconcile the free market economy with environmental sustainability. It relies heavily on "environmental stewardship", which typically values the natural world only in terms of its contribution to human well-being. It leave the environment detached from and irrelevant to the wider economy.
As Chancellor, George Osborne has resurrected the age-old argument that we need to choose between economic growth and the environment - despite stating  in 2009 that he had "always considered this to be a false divide" and that "economic growth and environmental sustainability can go hand in hand". He is the cheerleader for the outdated view amongst Tory MPs that the free market alone can satisfy the long-term needs of the economy.
For the reasons Miliband identified in his speech to the Social Market Foundation, an over-reliance on free markets - and their short-term priorities - is not a viable response to the challenges we face.
He has therefore been absolutely right to distinguish between "productive" and "predatory" capitalism. If it can underline the links between economic and environmental sustainability, Rio+20 will represent a valuable opportunity for the party to develop further examples of how it would tackle predatory capitalism.
It’s a chance to challenge the limitations of Tory economic orthodoxy. Most importantly, it’s a chance to start thinking about how the next Labour government can deliver long-term growth and sustainable wealth creation, while at the same time improving human well-being, creating jobs, ensuring fair and affordable access to resources such as water and energy, reducing inequalities, and tackling poverty.
Danny Stevens  is an independent environmental policy and political consultant and a Labour councillor in Hackney.
Tristan Stubbs  works on climate change and development policy at the Overseas Development Institute.