18/03/2015 06:03 GMT | Updated 17/05/2015 06:12 BST

The Treasury Must End Our Addiction to Fossil Fuels and Get Behind Clean Energy

George Osborne once said he had big plans for his term as Chancellor.

Big green plans.

Before the last General Election, he crowed that, under a Conservative government, no longer would the Treasury be "the cuckoo in the nest when it comes to climate change".

His party leader went further. Literally, in fact - because nothing says Green like flying all the way to the Antarctic to cuddle a husky.

David Cameron spoke of his 'greenest government' ambitions, dubbed climate change one of "the greatest threats" we face and backed the Chancellor's pre-election promises to clean up the economy, pledging to push for green jobs and make Britain "the most energy efficient country in Europe."

And he's not the only one.

Last year, Ed Miliband proclaimed tackling climate change was "the most important thing" he could do in politics.

In fact, climate appears to be a rare unifying factor for our party leaders. So last month, they pledged to work together across party lines to tackle climate change, acknowledging that climate change not only threatened the environment, but our security and economic prosperity, too.

Actions speak louder than words, and it's a shame theirs are falling so very short.

But today is Mr Osborne's moment. So what to expect from the once so Green Chancellor who's come to boast of wringing "every last drop" of oil from the North Sea?

True to form, the Autumn Statement threw its weight behind exactly that, with a tax cut for North Sea oil and gas.

Noting, however, that "there's still a lot of oil in there", he vowed to do still more for the industry. Lo and behold, the Infrastructure Act contains a duty to maximise the recovery of oil and gas - described to the Commons Environmental Audit Committee as "dangerous ".

If reports prove accurate, today's Budget will include yet more tax breaks for the sector.

The blinkered determination to drill for as much oil and gas as possible is completely at odds with the Government and official Opposition pledges on climate change.

Because here's the test: to avoid catastrophic climate change, the vast majority of our existing, conventional reserves of oil, coal and gas must stay underground and unburned. That's before you even start looking at the carbon locked up in unconventional fossil fuels like shale gas. You can quibble about the exact proportion: analysts at Carbon Tracker put the figure at around 80%; the International Energy Agency says it's around two thirds. But the science is clear. We have far more fossil fuels than we can safely burn.

At the Paris summit this December, party leaders have pledged to seek a fair, strong, legally binding, global climate deal which limits temperature rises to below 2ºC warming. They've likewise committed "to accelerate the transition to a competitive, energy-efficient low-carbon economy".

Action at home is vital to securing a global agreement in Paris - and public opinion is no excuse for inaction, with two thirds of respondents to a recent poll wanting a prime minister who takes the lead internationally on climate change. Moreover, solar and even wind power are consistently popular, with the latest government figures showing three quarters of Brits overwhelmingly support renewables.

Climate change threatens everything we hold dear, even if you're an economist. The business case for boosting investment in renewables and energy efficiency is incredibly compelling. Yet still the Chancellor seems hell-bent on hitching our economy to the dirty energy infrastructure of the past. The UK this month slumped to its lowest place for 12 years in the renewable energy attractiveness index for investors.

Osborne's backing the wrong horse. Ed Balls appears to be cheering it along. The UK has some of the best renewable energy sources in Europe - but we're harnessing a fraction of its potential. Sceptics often cite expense as an 'obstacle' to greater investment, yet the cost of renewable technologies is dropping fast. Reports suggest clean energy can now offer a greater return on subsidies than fossil fuels - the UK could and should leading on them globally.

It should be a scandal that, over the course of this Parliament, the UK government has splashed out more than 300 times more to support fossil fuels than clean energy overseas.

It's good news that the Swansea tidal lagoon project is taking another step forward today, but let's not forget the scandalous lack of support for cheaper, popular and immediately-scalable renewables such as solar PV and onshore wind. It goes nowhere near making this a climate literate budget.

And at the same time as handing out tax breaks for the fossil fuel giants, the Treasury's changing the tax rules in a way that threatens the future of locally-owned renewable energy coops, which should lie at the very heart of a clean energy system - one that's controlled by communities not multinational corporations.

Despite government cuts and policy instability, the renewables industry already supports more than 100,000 jobs. And a nationwide energy efficiency programme could create an additional 108,000 jobs every year between 2020 and 2030. It's estimated that the UK Green economy employs roughly one million people.

Home-grown renewable technologies mean less dependence on imports, more jobs, and greater stability in the long term. We have the technology and engineering capacity - it's the political will that's lacking. And the honesty to admit that you can't tackle climate change by increasing our dependence on and investment in on fossil fuels.

For the sake of our economy - and everything else that's threatened should we fail to heed the climate science and fail to keep most fossil fuels in the ground - as many unions say, we need a just transition to a zero carbon economy.

That means more jobs, but different jobs. It means retraining workers and redeploying our industrial and manufacturing expertise towards low carbon.

If the party leaders' climate pledge is worth the paper it's written on, the Treasury must end our addiction to fossil fuels and get behind clean energy.

So, here's what's topping my wish list on George's Big Day: let's put politics aside and have a cross party statement from George Osborne, Danny Alexander and Ed Balls on the risk of climate change to the UK economy - as well as the economic and employment benefits of a transition to a zero carbon economy.

What a sweet surprise that would be - and what true political leadership it would demonstrate.

Caroline Lucas is the Green Party MP for Brighton