On Wednesday I will join hundreds of others in Parliament Square to assert that we will not stand idly by in the face of climate breakdown and ecological crisis. We will affirm a commitment to engage in non-violent but illegal activities to try and force urgent action. Collectively we have signed a declaration to this effect; an Extinction Rebellion against the British government for criminal inaction.

Over decades we have all operated in our different spheres of life – whether as journalists, academics, politicians, campaigners and educators – to ring the alarm about the way planetary life support systems are being destroyed. But a powerful alliance of wealthy individuals and multinational corporations, backed by complicit politicians, has subverted the political process and blocked action. This is why, whoever we are and whatever we do, we are coming together now to say we are prepared to engage in civil disobedience to force urgent climate action.

We are prepared to halt lorries entering fracking sites; to stand in the way of bulldozers building roads and block traffic along heavily congested and polluted streets. Direct actions like these have a long and proud history; it’s time to carry them through in a systematic way to protect the climate, and to be willing to be arrested for doing so.

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So how have we have reached a situation where a law maker like me feels there is no alternative but to become a law breaker? Here my Quaker heritage is helpful. Our thin pamphlet of theological guidance ncludes the useful advice: “Respect the laws of the state but let your first loyalty be to God’s purposes.”

As a Quaker, I don’t believe that spiritual wisdom resides in books or rituals but in the still, small voice that tells you when something must change. When the inward light, that I believe we all have within us, prompts you to stand up to a fascist bully or to engage in civil disobedience to halt climate breakdown, you have no choice but to follow.

Facebook Twitter Pinterest in the budget, Philip Hammond threw £30bn at road building and gave a £3bn tax break to oil and gas companies. Photograph: Frank Augstein/AP

I represent some 5 million people in the European parliament. But who represents the generations as yet unborn that will have no chance of a decent and civilised life unless we act on climate change? Who represents the thousands of species that are becoming extinct during the modern era? A mass extinction that is entirely the result of human actions, and which we are living through almost without noticing?

I am proud of the way 50 Green MEPs, of 750 elected across Europe, have achieved policy breakthroughs. Just last week we won a vote on banning plastics and limiting the use of antibiotics on farms. And my work on sustainable finance has a real chance of creating financial incentives to shift investment away from fossil fuels and towards projects that will protect wild habitats.

But it isn’t enough. Green voters in the UK are grossly underrepresented because of our unfair electoral system. So British policy on energy and transport is stuck in the past, while other European countries with a strong green contingent in their parliaments are far more advanced in the transition towards a green economy.

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A spur towards direct action against this government and in defence of our planet conveniently appeared this week. As finance speaker for the Green party, I had called for an emergency budget for the climate, and the party issued a challenge: if the budget offers a single pound to climate-wrecking projects it will have failed.

Well, the chancellor didn’t mention climate change once in his statement, and, rather than action to avert climate breakdown, we saw the chancellor accelerate it. He threw £30bn at road building while freezing fuel duty for the ninth year running, meaning this now amounts to a £9bn tax giveaway a year. There was also a sneaky £3bn tax break for oil and gas companies in the North Sea, through the removal of “tax barriers” to investment. This was just the enticement we needed to take the government on.

The latest IPCC report and Tuesday’s Living Planet report by WWF, which reveals that wildlife populations have declined by more than half in less than 50 years, show how urgently change is needed.

It is no exaggeration to say that our survival as a species is at risk. Enough. Enough of words; of hypocrisy and broken promises. It’s time to act.

• Molly Scott Cato is Green party MEP for South West England