Countries that produce coal, oil, beef and animal feed have been lobbying to water down a landmark UN climate report, according to a leak of documents seen by Greenpeace’s investigation team.

Days before Cop26, the international climate change negotiations taking place in Glasgow, the leaks show fossil fuel producers including Australia, Saudi Arabia, Iran and Japan are lobbying the Intergovernmental Panel on Climate Change (IPCC) to remove recommendations that the world needs to phase out fossil fuels.

According to the documents, the Organization of the Petroleum Exporting Countries (Opec), which includes countries such as Iraq, Kuwait, Libya, Nigeria, the United Arab Emirates and Venezuela, also backed weakening the report’s recommendations on fossil fuels.

Meanwhile, large meat and dairy producers such as Brazil and Argentina reportedly attempted to change messages about the climate benefits of promoting plant-based diets, according to the leak of more than 32,000 comments by governments, corporations, academics and others on the draft report of the IPCC’s working group III, which looks at measures to protect the globe from rising temperatures.

Climate scientist Simon Lewis, a professor of global change science at University College London, told Unearthed: “These comments show the tactics some countries are willing to adopt to obstruct and delay action to cut emissions.

“On the eve of the crucial Cop26 talks there is, to me, a clear public interest in knowing what these governments are saying behind the scenes.”

He added: “Like most scientists I’m uncomfortable with leaks of draft reports, as in an ideal world the scientists writing these reports should be able to do their job in peace. But we don’t live in an ideal world, and with emissions still increasing, the stakes couldn’t be higher.”

The IPCC said its processes were designed to guard against lobbying and that in order to do this it used “diverse and balanced author teams, a review process open to all, and decision-making on texts by consensus”.

Prof Martin Siegert, the co-director of the Grantham Institute at Imperial College London, said the report exposed the behaviour of certain countries that have attempted to hold back progress on decarbonisation.

“This lobbying has no impact on the scientific credibility of the IPCC report, however. That the IPCC upholds the science in the face of such forceful vested interests is a triumph, and we should be grateful to the scientists involved for not yielding to such pressure,” he said.

“Be under no illusion, decarbonisation at the level we need to avoid dangerous climate change will be opposed by some, perhaps many, in the fossil fuel industry and by a number of people, companies and nations that benefit financially from fossil fuels.”

Mark Maslin, a professor of earth system science at University College London, said: “Countries have always been encouraged to comment on all the IPCC climate change reports. Many countries take this as an opportunity to lobby the scientists to change their conclusions – for example Australia wanting to support coal, Saudi Arabia wanting to support oil, Russia natural gas and Brazil beef production.

“But it has no effect on the reports. Scientists, social scientists and economists that work on these reports are led by the evidence and what is best for the world and all of its peoples. This is why the public and politicians all around the world trust scientists and the IPCC reports as they know they will not be influenced by petty politics.

“The lobbying also drives home what we need to do to reduce climate change: stop using coal as soon as possible, phase out oil and natural gas usage as soon as possible, stop deforestation and start reforestation and move to a more plant-based diet and definitely cut down the amount of beef we produce. Not only will this reduce our carbon emissions but it will save millions of lives due to massively improved air quality and diet.”

Cop26, which begins at the end of the month, will see representatives from most of the world’s countries gather to agree on measures to tackle the climate crisis.

Delegates are being asked to do their bit to uphold a global heating target of 1.5C above pre-industrial levels in order to avoid the most serious and irreversible damage to the planet.