The UK will seek a global coalition to push for climate action after a fractious end to UN climate talks in Azerbaijan, the UK energy secretary, Ed Miliband, has pledged.

The Cop29 conference ended on Sunday with a deal promising $300bn in finance for developing countries by 2035, which critics called a “failure” and “betrayal”.

Miliband played a key role in the talks, attempting to bridge divisions between the rich and poor world in the hectic closing hours, late on Saturday night. He has vowed to continue working over the next year, ahead of an equally important summit in Brazil next November.

“This alliance of high ambition is the world’s centre ground of climate politics and is the best hope for the future. In our work with Brazil, hosts of Cop30, we are seeking to demonstrate this in practice,” he wrote in the Guardian.

Miliband has argued that forging a global coalition to tackle the climate crisis, and providing finance to the poor world, are in the UK’s interest.

“This idea is 100% in Britain’s self-interest,” he told journalists after Cop29. “I think there is a great British tradition of ensuring that we play our part in helping vulnerable countries who are exposed to climate change. Our estimates in the department say that [the $300bn of climate finance by 2035] could help protect up to a billion people [from] some of the effects of climate change and also on mitigation.”

At Cop30 in Brazil, countries will expected to produce new plans for cutting greenhouse gas emissions. Miliband hailed the UK’s recent pledge of an 81% reduction in emissions compared with 1990, and vowed to work with Brazil on energy, finance and forests over the next 12 months.

Also writing in the Guardian, the president of Cop29, Mukhtar Babayev, criticised developed countries for the fractious end of Cop29, and claimed that China would have offered climate finance voluntarily if rich countries had shown more of a lead.

Babayev, Azerbaijan’s environment minister, blamed rich countries for failing to stump up enough cash for the developing world and nearly collapsing the talks by only making key concessions too late in the process.

By contrast, he said, “China spent the full two weeks coordinating their response to the negotiations in a regimented fashion with the G77 group of the world’s poorest nations. The Chinese were willing to offer more if others did so too (but the others didn’t).

“Their target of $500bn for the industrialised world’s contributions alone still would not suffice to limit global warming to 1.5C, but it was a more acceptable minimum figure – something publicly acknowledged by Kenya and several other African nations.”

China is classed as a developing country under the ​UN climate process, which means it carries no obligation to provide finance to poorer countries, while the rich economies do.

At Cop29, rich countries demanded that the donor base should be broadened to include emerging economies such as China and petrostates such as Saudi Arabia.

China did not object to the Cop29 deal and pointed to billions it was providing to the poor world already, mostly in the form of loans, in what is known as “south-south cooperation”. Developed countries were keen to point out that the deal struck allowed for China to contribute, while stipulating that ​t​he developed world should take the lead.

Babayev described the final moments of what he termed the “Baku breakthrough”, which came 35 hours after the official deadline. An earlier offer by developed countries to supply $250bn a year to the developing world by 2035 was widely derided but rich countries were unwilling to increase it.

He noted that it took pressure from the presidency to force the EU to increase its deal​ beyond the originally proposed $250bn.

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He also wrote: “It was a mistake for western countries to insist that the final draft deal – and particularly the draft financials – was not unveiled until the penultimate day. To the global south, this rightly made it look like a fait accompli. My negotiating team argued vociferously for drafts to be made public far earlier. But that was not to be.

“Early in the negotiations it became clear that certain western voices would not shift,” he added. “That position was not universal: the new British government has reassumed the country’s role in global climate leadership, and that was clearly in evidence at the summit itself, with new UK targets on decarbonisation and net zero.”

The deal “almost didn’t happen”, Babayev said, but Azerbaijan stepped in to push the rich world to make its final $300bn offer.

Some veterans of the talks described Babayev’s views as “fake news”, “hypocritical” and “sliding off the edge of the planet”.

“The small island states and least developed country walkout on the Azerbaijani presidency was not because the presidency was supporting them, but because it was not,” said Bill Hare, the chief executive of the Climate Analytics thinktank.

“This is just one illustration of the way in which it is clear the presidency was not supporting the interest of the vulnerable countries. When the presidency talks about the global south, we know that this means the Like-Minded Group of Developing Countries negotiating bloc, [led by] Saudi Arabia and China, and does not include the interests of the vulnerable countries.”

He added: “The final deal was possible because of the alliance that developed between the European Union, the small island developing states, least developed countries and others – and not because of anything the presidency did, in fact quite the opposite. From the beginning, the presidency was quite opposed to any kind of decent outcome.”

Developing countries should receive at least $1.3tn a year by 2035 under the deal, but much of this is likely to come in private-sector investment, with an unspecified amount also coming from potential new levies, such as taxes on fossil fuels, frequent flyers and shipping.

There was heavy criticism of the Cop presidency at the talks. Several countries told the Guardian that the presidency did not appear to be in control of the process, asked other countries for assistance that was then ignored, and was unavailable at key moments.

India said after the gavel had come down on the deal that it was unhappy with the outcome. Chandni Raina, the lead negotiator for India, called the deal a “travesty of justice”.