The process of UN climate negotiations is no longer fit for purpose and requires a comprehensive overhaul, leading experts have warned.

The group of prominent scientists, advocates and policy experts said countries that do not support the phase out of fossil fuels in energy systems should not host future summits – or conference of the parties (Cops).

Among those who signed the open letter on the fifth day of Cop29 in Azerbaijan were former UN secretary-general Ban Ki-moon, former executive secretary of UN Climate (UNFCCC) Christiana Figueres and former Irish president Mary Robinson.

They warned UNFCCC head Simon Stiell of limitations to the the existing Cop process, which aims to drive the rapid, large-scale changes urgently required to limit warming to the 2015 Paris Agreement goals to limit dangerous global warming.

The letter acknowledged significant advances that have been made during Cop summits, including the landmark Paris climate agreement.

But the signatories said: “It is now clear that the Cop is no longer fit for purpose. We need a shift from negotiation to implementation.”

The call comes after Ilham Aliyev, president of Cop29 host country Azerbaijan, told the summit earlier this week that oil and gas is a “gift” from God.

An investigation reported by the BBC also found that a Cop29 official tried to use the event as an opportunity to advance fossil fuel business deals, while concerns are growing over the imprisonment of climate defenders in the country.

Sandrine Dixson-Decleve, executive chair of Earth4All who signed the letter, said: “We need a Cop process that offers delivery, not delay.

“We demand Cops that are platforms for government and stakeholder ambition, not enablers of fossil energy contracts and growing greenhouse gas emissions.

“After 28 Cops, time is up on negotiations that don’t foster action and implementation. Planetary stability is dependent on equality, justice and poverty alleviation to address the greatest existential challenge of our time.”

The call for reform also comes on the heels of reports warning of increasing global carbon emissions, the degradation of carbon sinks, and unprecedented climate-related human and economic losses.

The letter signatories warned that the world can no longer exclude the possibility of surpassing 2.9C of warming by 2100.

Ms Figueres said: “At the last Cop, fossil fuel lobbyists outnumbered representatives of scientific institutions, Indigenous communities and vulnerable nations.

“We cannot hope to achieve a just transition without significant reforms to the COP process that ensure fair representation of those most affected.”

PA has contacted the UNFCCC for comment.