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."
The UK, which is hosting the talk in Glasgow, has 230 registered delegates.
So what counts as a fossil fuel lobbyist?
Global Witness, Corporate Accountability and others who have carried out the analysis define a fossil fuel lobbyist as someone who is part of a delegation of a trade association or is a member of a group that represents the interests of oil and gas companies.
Overall, they identified 503 people employed by or associated with these interests at the summit.
They also found that:
- Fossil fuel lobbyists are members of two country delegations, Canada and Russia
- The fossil fuel lobby at COP is larger than the combined total of the eight delegations from the countries worst affected by climate change in the past 20 years
- More than 100 fossil fuel companies are represented at COP, with 30 trade associations and membership organisations also present
- Fossil fuel lobbyists dwarf the UNFCCC's official indigenous constituency by about two to one
One of the biggest groups they identified was the International Emissions Trading Association (IETA) with 103 delegates in attendance, including three people from the oil and gas company BP.
According to Global Witness, IETA is backed by many major oil companies who promote offsetting and carbon trading as a way of allowing them to continue extracting oil and gas.
"This is an association that has an enormous number of fossil fuel company as its members. Its agenda is driven by fossil fuel companies and serves the interests of fossil fuel companies," Mr Worthy said.