There are more delegates at COP26 associated with the fossil fuel industry than from any single country, analysis shared with the BBC shows.
Campaigners led by Global Witness assessed the participant list published by the UN at the start of this meeting.
They found that 503 people with links to fossil fuel interests had been accredited for the climate summit.
These delegates are said to lobby for oil and gas industries, and campaigners say they should be banned.
"The fossil fuel industry has spent decades denying and delaying real action on the climate crisis, which is why this is such a huge problem," says Murray Worthy from Global Witness.
"Their influence is one of the biggest reasons why 25 years of UN climate talks have not led to real cuts in global emissions."