Under this Coalition government, the Foreign Office has a renewed sense of mission. It is a mission to promote Britain's national interest, while tirelessly working for a world which is more secure, more stable, more free and more prosperous.

In no area is this more relevant than the fight against climate change. Today ministers from more than 20 countries will meet in London with the goal of speeding up global progress on clean energy. I am in no doubt that we must meet this challenge, not only to safeguard the sustainability of our planet and the security of our energy, but also to ensure we are at the front of the queue when it comes to the jobs and industries of the future.

We are at the start of a global shift from a high- to a low-carbon economy. The shift will be driven by those countries that transform their own economies so as to better compete in rapidly expanding global markets.

The scale of ambition from some of our competitors is awe-inspiring. Denmark aims to generate half its electricity from wind by 2020. China is investing $1.7 trillion in the low carbon economy over five years. Germany is pursuing an unprecedented transition in energy through innovation in renewable electricity, energy efficiency and green infrastructure.

These policies are driving rapid structural change in the economies of our major partners. They are reshaping markets that are crucial, both as destinations for our exports and sources of inward investment, for the UK commercial diplomacy that has been revitalised under this government.

But the risks are growing too. We have left behind an era in which energy, food, water, and other resources have been relatively cheap and plentiful. Rising demand is carrying us into an age of higher and more volatile prices for energy, food and raw materials. Political tensions in the regions traditionally supplying the world's oil have added to the uncertainties. Climate change is amplifying these stresses, and will do so increasingly.

These risks post a serious threat to growth, through price shocks and inflation. Their political consequences could be more serious still, with some tempted to see a zero sum competition for resources between consumers and between nations. That would be an historic mistake, triggering a spiral away from the cooperation based on agreed rules that is vital for a globally exposed economy like our own, towards a much more dangerous world of fragmentation, competition and greatly enhanced risks of conflict.

A core goal of British foreign policy must be to defend the open global economy against this threat. That will require a rapid global shift towards enhanced resource productivity and energy efficiency, and lower carbon intensity. Encouraging this transition, not least working through the strengthened bilateral partnerships that we have been building especially with the emerging economies, is a top priority for our diplomatic network.

Britain can and must play a leading part in the transition through its domestic policies too. Our need for an export-led recovery and for inward investment in modern infrastructure is well known. One of the biggest drivers of that export-led recovery will be the green economy. There is unprecedented global demand for green innovation, which could provide an enormous boost to UK industry in the years to come. Thankfully, actions taken across government will mean Britain is well placed in the decades to come.

At BIS, the Green Investment Bank - first proposed by George Osborne in 2009 - is now becoming a reality, with £3 billion of public investment set to unleash £15 billion of private money.

At DECC, the Green Deal promises to be the biggest home improvement programme this country has ever seen, transforming energy efficiency - and lowering bills.

At Defra, measures to preserve and enhance biodiversity, alongside determined efforts to stimulate green growth, are putting the natural environment back at the top of government priorities.

As Foreign Secretary, when trying to persuade other countries, both advanced and developing economies, to go green, it is a huge advantage to be able to point to the example we are setting at home.

Without this green record, it is doubtful we could have achieved so much at the Durban conference last year. It is to the UK's great credit that our leadership helped persuade the major emerging economies to acknowledge that they too will have to adopt legally-binding targets for carbon emissions. We must stay the course at home if we are to maintain our influence and reach a new global agreement in 2015.

Energy security is another essential part of this mix. Our reliance on expensive and volatile fossil fuel imports is damaging to our economy, and will only get worse without concerted action. The transition will not be easy, but for the sake of our long-term security and prosperity, we must wean ourselves steadily off this resource, and turn instead to low carbon alternatives.

David Cameron's great ambition to lead the 'greenest government ever' relies heavily on a Britain that is leading the way on the world stage, pressing for determined and united global action, setting an example to other nations, cajoling those who do worse and aspiring to match those who do better. I can proudly say that the Foreign Office is leading this charge with vigour.

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