Any lingering pretence that David Cameron or George Osborne represent a form of "modern compassionate Conservatism" was finally extinguished by last week's Autumn Statement. They have committed themselves to cutting the state back to the same size as our share of national income as it was 80 years ago – before the NHS and the 1944 Education Act established rights that define us a civilised country.
The Tory project for a second term appears to be born from ideology, not from the necessity of cutting the deficit and balancing the books. Over the days, weeks, and months to come, the Labour Party will have much more to say about the choice facing Britain at the next election as a consequence of this dire economic experiment.
But tomorrow, on the other side of the world, British ministers will be joining negotiations in Lima that can have equally profound consequences for our country and the whole world.
The issue being discussed also symbolises, just as much as the Autumn Statement, Mr Cameron's long retreat from the principles in which he once claimed to believe.
The United Nations climate change talks in Lima ahead of next year's conference in Paris will probably not get the attention they deserve. But they are our best chance yet to secure a binding international agreement to limit greenhouse gas emissions.
They are crucial to anyone who cares about our economic future, the environment our children will inherit, and, as the floods last winter showed, the national security of our country.
Indeed, no amount of promises last week for belated finger-in-the-dyke funding to protect homes can hide how the millions of families in Britain, as well as billions around the world, face an insecure future because of climate change.
Like other EU countries, Britain has signed up for 40 per cent reductions in carbon emissions by 2030. But the leadership and political consensus we once offered the world have been replaced by dither and denial.
When I was in the last Labour Cabinet, I was grateful to both the Tories and the Lib Dems for backing our Climate Change Act. Those were the days when Mr Cameron was busy changing the Conservative Party's logo to a tree, travelling thousands of miles to pose for photo opportunities with a husky on a glacier and promising to lead the "greenest government ever".
Since becoming Prime Minister, however, he has tried to sell off the nation's forests, deterred investment in renewable energy, and declared he wanted rid of "the green crap" altogether.
Ahead of these talks in Lima, the Prime Minister has ignored pleas from the Foreign Office to raise climate change in his recent meetings with Chinese leaders.
But there is a real opportunity to take a decisive step on the path we set out on at the Copenhagen conference in 2009. The United States, the EU and, most importantly, China, are all showing a willingness to act. If negotiations succeed, they will create for the first time a global climate regime for all countries.
From my own experience, I know that the negotiations are difficult: you need clear principles and there must be real diplomatic engagement including a willingness to listen to other countries' views.
So if I were Prime Minister, here is what I would do.
First, we would seek to raise our ambition to meet the scale of the challenge. In the past five years, the scientific evidence of climate change has got stronger, not weaker, even as the Government has allowed the political consensus around action in the UK to fray. In Lima next week and in Paris next year, a Labour government would be pushing for global targets for reducing carbon emissions that rise every five years with regular reviews towards the long-term goal of what the science now tells us is necessary – zero net global emissions in the latter half of this century.
Second, we would engage through every diplomatic channel and at every opportunity to ensure the whole world faces up to this great threat hanging over humanity. We would demand that climate change is on the agenda of every international summit in the run-up to Paris. And leaders visiting Britain during the next government can be certain that action on climate change will always be on the agenda.
Third, we would lead by example, not follow in the wake of others. Under the last Labour government, Britain was the first country in the world to enshrine a long-term emissions target into law. Under the next Labour government, we will commit Britain to making our electricity supply carbon free by 2030.
Fourth, we will not make the economy an excuse for dragging our feet on climate change. That there was no mention of climate change in the Chancellor's Autumn Statement tells you all you need to know about where this issue now sits in the Government's priorities.
There is no trade-off between building a recovery which works for most people and resetting the energy market to keep household bills low, creating new high-skill, high-wage jobs which can help to pay down the deficit, or investing in green technology which can power Britain's economy forward into the future.
The last Labour government helped to create new markets for thousands of British companies and more than a million new jobs in the green sector. This Government has sabotaged new investment through a combination of uncertainty and internal Tory party politics where too many of its MPs are flirting with climate change denial.
My goal is to have the ambition matched with certainty for Britain to be a world leader in green technology by 2025, creating another one million new jobs.
The environment may not be as fashionable an issue now as it was when David Cameron attached a wind turbine to his house. But I believe tackling climate change is the most important thing I can do in politics for the long-term future of my kids and their generation.
And I will not leave those principles behind at the door to Downing Street. That is the choice the country will face at the next election. A Conservative government that abdicates its responsibilities and makes Britain a laggard on climate change. Or a Labour government that leads.
Ed Miliband is the leader of the Labour Party
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