The UK's efforts to establish a worldwide coalition on climate action will be spearheaded by a former World Bank climate chief, as the Guardian can reveal.

As the UK's climate ambassador, Rachel Kyte—a former vice president of the World Bank and special representative for the UN—will spearhead the country's comeback to the forefront of international climate diplomacy.

Her contribution will be crucial to the promise last week made by Foreign Secretary David Lammy that, unlike the previous administration, which he referred to as "climate dinosaurs," the UK would take the lead in addressing the environmental and climatic issues.

To the indignation of campaigners and dismay of foreign governments and allies, Rishi Sunak removed the envoy function. Sunak also skipped global climate conferences.

Kyte is well-liked by governments in both developed and developing nations. She has experience attending international climate summits and was most recently a lecturer at Oxford's Blavatnik School of Government. During her tenure as the CEO of the Sustainable Energy for All initiative, she collaborated with numerous of them.

Kyte told the Guardian: “This government is committed to reconnecting the UK to the world with climate action as a priority. And the world is being shaped politically and economically by climate change. This provides an opportunity to use international action to help deliver on the UK’s energy mission. And it provides challenges, not least in mobilising the financing to protect people and drive greener growth. There is no time like now for the UK to help drive action and I am excited to play my part in this new role.”

Lammy and Ed Miliband, secretary of state for energy and net zero, will announce the appointment on Wednesday at New York climate week, where they are hosting an event on building a global clean power alliance.

Miliband will hold discussions with other governments on the need for vastly increased pledges of climate finance to the developing world. Poor countries want assurances that they will receive at least $1tn a year in assistance to help them cut greenhouse gas emissions and cope with the impacts of climate breakdown.

Climate finance will be the main topic of what are expected to be fraught discussions at the next UN climate summit, Cop29, in Azerbaijan. Miliband will lead the UK’s negotiations himself, in contrast with the previous government, in which it was left to junior ministers.

The diplomatic charm offensive has already begun, as Miliband welcomed the president of Cop29, Mukhtar Babayev, to London in July, and in August made an extensive trip to Brazil, which is the current president of the G20 group and host of next year’s Cop30 climate summit.

Lammy will also, with environment secretary Steve Reed, appoint a nature envoy for the first time, to push for global action on protecting the natural environment, as the Guardian revealed last week. That appointment is not expected until next month.

Kyte, whose official title will be UK special representative for climate, will coordinate the UK’s relations with other donor countries, as well as forging alliances with the poor world, and with the economic giants of the developing world, China and India.

Her appointment was welcomed by climate experts and campaigners. Edward Davey, UK head of the World Resources Institute thinktank, said: “Rachel is a giant and a ball of fire, with a vast hinterland of knowledge and experience and a global network of friends and allies. She will be brilliant and a force to be reckoned with.”