If you believe that unrestrained capitalism is the solution to our planet’s environmental and social challenges, or that democracy is enhanced by two major parties bickering about personality and management style, then you are currently well served by the Liberal, National and Labor parties and might choose not to read on. If you think there might be better ways to make the planet more sustainable, just, peaceful and democratic, then there is certainly a place for you in the Greens.

The Greens party was founded on four broad principles of ecological sustainability, social justice, participatory democracy, and peace and nonviolence. Over the past 20 years those principles have guided the party in campaigns as diverse as ending the logging of native forests, defending and participating in local government, tackling climate change, opposing war and promoting more progressive policies on public education, industrial relations, taxation and welfare.

However the principles don’t answer every political issue by themselves. They don’t tell us the best way to reduce carbon emissions, they don’t endorse or condemn capitalism, they don’t say if we should have an inheritance tax and they don’t tell us how to end animal cruelty. These are all issues where there is room for debate within the Greens. From forest defenders to middle-class doctors and student activists, the Greens party is a broad and accepting social movement that has always celebrated its diversity.

This is why it is pretty hard to understand all the anger being expressed at the establishment of a small, self-organising group within the Greens that calls itself Left Renewal.

Left Renewal members believe that capitalism is a major problem and express a belief in socialism and collective enterprise. They don’t much like the state and want grassroots collective decision-making and reduced police powers. In its blanket opposition to capitalism and denunciation of state power, Left Renewal goes much further than most Greens members are comfortable with.

Just to be clear, neither of us are members of Left Renewal. Having read the group’s opposition to top-down decision-making, it probably wouldn’t have us if we tried. The group certainly steps beyond what either of us believes both economically and politically. However, what it is putting forward is one of many views that is consistent with the Greens’ four principles and is a legitimate contribution to political debate in the party.

Left Renewal has every right to exist in the Greens along with less obvious, but no less real, rightwing groupings in the party. It is perfectly natural for like-minded people in a party to coalesce and seek to achieve common goals. It’s equally natural for people to seek to build bridges internally and adopt more moderate or conciliatory positions. A healthy political party will have all these elements and be able to contribute to broader debates about how society should work.

Before the mid 1980s and the political ascendancy of neoliberalism in Australia’s state and federal parliaments, this country had a much more moderate economic position. It was common political ground that Australia should have a mixed economy with distinct roles for the private market as well as for public ownership and public enterprise. We had publicly owned banks which delivered profits back to government, public ports and railways that stitched our cities, towns and regions together, and a public health and education system that delivered for everyone to world-class standards.

We still have elements of this but they survive on borrowed time in the face of unrelenting political attacks from both the Coalition and Labor. As members of the Greens, we are happy to place a stake in the ground and say we will always support public before private education and public health over private hospitals. However if we are going to make the place fairer and more sustainable we need to support public and social enterprise more broadly.

Of course capitalism has an extraordinary capacity to organise resources and innovate. Whether it is delivering the iPhone or Facebook, cornflakes or solar panels, there is an energy and creativity in capitalism that anyone can see and we support. But capitalism has also put our planet in danger, as the conditions for life are degraded by an economy in which fossil fuels, profit and the market reign supreme.

Markets can’t price a species and they don’t know the value of compassion. They don’t respect the fact that we have a finite planet with finite resources. Markets only respect customers with money, not citizens with rights or a planet in need.

That’s why it is well and truly time to openly reject neoliberalism and the major parties’ uncritical acceptance of market-based solutions to literally every challenge we face.

Let’s remember how in the 1950s Australia led the world with the publicly owned Snowy Hydro scheme for renewable energy. We are a lot richer now than we were then so there is no question that we can build the 21st century public solar and windfarms we need to end our reliance on coal.

It’s time the public stopped subsidising corporations to destroy our native forests and that we redirected the billions of tax dollars from private educators to public schools and Tafe. We can discuss how to future-proof fair internet access by retaining the NBN in public hands. Perhaps we can remember how to tax the rich while we are about it?

In short, we need to come together as a society and say that people are more than customers and our natural world is more than a collection of exploitable resources. We need transformative change. Parliamentarians and elites passing laws and changing government programs cannot alone deliver the level of change that is needed. As always positive change will come about only when grassroots movements have sufficient momentum to drive that change.

If this makes our current leaders uncomfortable then that’s hardly a surprise. It’s about challenging and changing the status quo and that, surely, is what the Greens are here for.