The United Kingdom is a critically important actor in the global fight against climate change.

As a permanent member of the UN security council, and a member of the G20 group of leading industrialised economies, it is well placed to further a progressive climate agenda and influence other states to fully implement commitments made under the Paris agreement.

Decarbonisation is a vital part of this agenda. The UK has made important progress in this regard; in April 2017, it enjoyed its first full day without any coal-fired electricity since the 1880s, which was a striking achievement for a country that had been at the vanguard of the Industrial Revolution.

As the prime minister, Theresa May, said last year: “We can be proud of our success in facing up to the reality of climate change, but we are not complacent about the action needed to sustain that success in the future.”

The best way for any country to avoid climate complacency is to develop robust, holistic and people-centred policies across government, so short-term trade or financial priorities do not trump the wider imperative of cutting global emissions.

The UK now faces a crucial opportunity to live up to the prime minister’s words and prove it is serious about phasing out the use of fossil fuels worldwide, and not only on its own territory.

The UK parliament’s environmental audit committee is currently holding an inquiry into UK Export Finance’s (UKEF) financing of fossil fuels in developing countries. This government agency provides financial support for international trade with the aim of boosting British companies’ exports.

It is deeply concerning to note that over the period 2010-2014, UKEF provided more than 99.4% of its energy finance to fossil fuels, and less than 1% to renewable energy.

Over the longer timeframe of 2010-16, it is estimated that UKEF provided £4.8bn of support for fossil fuel projects. The UK’s total spend on its International Climate Fund for a similar period, 2011-17, was £4.9bn.

These figures and policies are hard to reconcile with the UK’s commitments under the Paris agreement, its membership of the Powering Past Coal Alliance and its own pledge in 2013 to end support for public financing of new coal-fired power plants overseas.

They are also at odds with the view of the governor of the Bank of England, Mark Carney, who warned in 2014 of the stranded asset risk inherent in fossil fuel projects.

The time has come for the UK to change course, in the interests of the whole world.

Research indicates that a third of oil reserves, half of gas reserves and over 80% of current coal reserves need to remain in the ground in order to meet the target of 2C of global warming.

But as the recent report by the Intergovernmental Panel on Climate Change set out so starkly, our target must be 1.5C if we want to avert irreparable damage to our planetary ecosystem – so even more radical action against fossil fuels is required.

Meeting these challenges can only be done collectively, in a spirit of international and intergenerational solidarity under the framework of the United Nations.

I was UN secretary general when the Paris agreement was signed, and the sustainable development goals agreed. I valued the UK’s contributions and commitment to both these vital multilateral achievements, and continue to believe the country can play a transformative role in shaping the global climate agenda.

As deputy chair of the Elders I continue to call on G20 nations to move away from fossil fuel investment, and I believe the UK can play a leading role in this crucial move.

I encourage the UK government to recalibrate its export finance policy so it is fully consistent with international climate trends and obligations.

Promoting fossil fuel investments abroad locks in high-carbon infrastructure in developing countries for years to come, which is the opposite of sustainable development.

There is now a growing consensus that fossil fuels should not be funded in any way by export finance organisations.

The World Bank Group has already ended its finance to upstream oil and gas; the European Bank for Reconstruction and Development recently ended finance to coal; and the Swedish Export Credit Corporation has announced it is going fully fossil-free.

UKEF and the wider UK government should use the occasion of the parliamentary inquiry to demonstrate a clear shift in policy away from fossil fuels and use its investments to support clean energy.

If the UK takes these necessary steps, it can be at the forefront of the transition to a low-carbon economy. I look forward to seeing its government, industries and people rising to this challenge.