Over 50 cross-party MPs and peers have written to the prime minister with demands they see as critical to ensuring the United Nations summit in Dubai is the "moment that current and future generations need it to be".

They want the UK to use its influence to bring about the "end [of] the fossil fuel era by urging the phase out of coal, oil and gas," they said in the letter, shared with Sky News.

The document also urged Mr Sunak him to reinstate a UK climate envoy to ensure Britain's interests are "fully represented" at the talks - just as John Kerry does for the US.

Rishi Sunak plans to attend this year's summit in person, along with energy security secretary Claire Coutinho.

The government said it will use COP28 to promote the UK's success on climate action and use it to "help others".

But the PM's commitment to climate action has been questioned recently after he green lit the new Rosebank oil field, handed out new oil and gas licences, and rowed back on some key climate targets.

He is also reportedly planning to use the King's Speech on Tuesday to double down on anti-green policies.

The government's "commitment to bold climate action has come under scrutiny in recent months", the letter said, but added: "UK leadership has never been more critical."

Conservative peer Zac Goldsmith, one of only two Tories to sign the letter along with Pauline Latham MP, said the UK must use its "hard won status" as a global climate leader to "leverage ambition from other countries".

Lord Zac resigned as a minister in June in protest of the government's "apathy" towards the environment.

COP28 in December will round off a year that is on course to be the hottest on record, with high temperatures exacerbating wildfires in Europe, heatwaves in the UK, and flooding in the US.

The letter was signed by members from all major parties, though primarily by Labour figures, and was organised by the Climate All Party Parliamentary Group (APPG).

The Climate APPG chair, Green Party MP Caroline Lucas, said: "After a year of devastating climate impacts around the world, our planet can't afford an unsuccessful outcome at COP28."

What do the MPs want from the PM for COP28?

The letter asks the UK to persuade other countries to sign up to a commitment to "phase out" fossil fuels.

Perhaps surprisingly, this target has proved very incredibly contentious at previous COP summits, at which countries are supposed to agree collective next steps to tackle climate change.

The commitment gained strong traction last year at COP27 in Egypt, with support from 80 nations inducing the UK.

But it was forced out of the final political agreement by countries that are big polluters or rely on fossil fuel revenues, including petro-state Saudi Arabia.

Last month, climate minister Graham Stuart last month said the UK would push for a phase out of "unabated" fossil fuels, which allows for fossil fuels to be burned as long as the emissions are also captured.

Carbon capture technology remains expensive and few projects are running globally at scale.

The signatories say a plan to triple renewable power will help the world ditch the fossil fuels, which are responsible for the vast majority of global warming.

In a landmark moment last month, the world's leading energy group, the International Energy Agency, forecasted for the first time that demand for oil, gas and coal would all peak before 2030, declaring the "beginning of the end" of the fossil fuel era.

The parliamentarians also want the PM to restore the UK climate envoy ministerial role, that had been held by MP Alok Sharma before the PM axed it.

"This role has been critical to demonstrating the government's political focus on climate, accessing key global players, and working to further the UK's international climate goals."

A key success at last year's COP27 talks was countries agreeing to set up a fund to pay for climate damages in developing countries, which tend to have contributed the least towards climate change.

The MPs want the UK to help get the fund up and running with cash actually flowing into it.

A government spokesperson said: "Tackling emissions is a global challenge, and no major economy has gone faster than the UK.

"We were the first country to legislate for net zero and we have cut emissions faster than any other G7 nation.

"The prime minister and the energy security secretary will be attending COP28, representing these world-leading achievements and promoting our ambitious climate change targets while using what we have learnt to help others."

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