Britain is to host a crunch climate conference next year at which the future direction of global efforts to avert the climate crisis will be determined, the government has confirmed.

The COP26 meeting, under the auspices of the UN, will take place in Glasgow in December 2020, with about 30,000 delegates expected as well as leaders of most of the world’s governments, making it the biggest international summit to be hosted in the UK.

After months of behind-the-scenes preparations, the UK was confirmed as co-host with Italy, where some preparatory meetings will take place, when other countries signalled their acceptance on Tuesday.

The announcement shines a spotlight on the UK’s diplomatic standing on the world stage after Brexit and will bring intense scrutiny of the British government’s actions on the climate emergency.

Before her departure, one of Theresa May’s final acts as prime minister was to enshrine in law a commitment to ensure the country had net zero carbon emissions by 2050.

Dominic Raab, the foreign secretary, said: “The UK has just received a huge vote of confidence from our international partners. We’re ready to bring the world together to make sure we leave our previous environment in a better state for our children.”

Kicking off the government’s global diplomatic push, which will encompass developing as well as developed countries, the Department for International Development said British overseas aid had helped poor and vulnerable nations cut their greenhouse gas emissions by 16m tonnes in the past eight years, the equivalent of taking 3m cars off the road for a year.

These included projects to provide clean energy in Kenya, Rwanda and Mali, and helping farmers grow climate-resilient crops or put in measures to save water.

Alok Sharma, the international development secretary, said: “This nomination [to host COP26] is testimony to the UK’s leading role in the fight against climate change. UK aid has helped millions of people in developing countries to access clean energy and prepare for the impacts of climate change.”

Civil society groups and businesses also called for the UK to take action on its net-zero commitment as part of the hosting role.

Tanya Steele, the chief executive of WWF UK, said: “This is a real opportunity for us to showcase our vision of a greener future, powered by renewable energy, with flourishing sustainable industries and a restored natural world.

“But if we want other countries to follow our lead, we will have to be able to show that we have backed our bold commitments with concrete action.”

Stephanie Pfeifer, the chief executive of the Institutional Investors Group on Climate Change, said: “The UK should use its diplomatic influence to encourage other countries to make similar pledges [to reduce carbon to net zero] in the run-up to the summit to ensure it’s a success.”

However, some experts are worried Brexit will distract ministers and officials from climate issues.

The conference will be the most important on the climate since the Paris agreement was passed in 2015, because the future of the pledges countries made will be reviewed.

Nations agreed to a legally binding commitment in Paris to keep global temperature rises to no more than 2C above pre-industrial levels, but also offered national pledges to cut or curb their greenhouse gas emissions by 2030.

Those pledges were insufficient to meet the 2C requirement, so governments will be expected to come up with more ambitious offerings in 2020.

Progress made to date will also be assessed. Most countries, including the US, China, India and the UK, as well as the EU, have national or bloc-wide pledges to cut or curb greenhouse gas emissions growth by 2020, agreed before Paris, so auditing whether these are met will be a key aim.

Probably the most watched effect on the talks, however, will be the outcome of the US presidential election, which takes place on 3 November 2020, weeks before the conference. Donald Trump has begun the process of withdrawing the US from the Paris agreement, but withdrawal cannot legally take place until 4 November next year.