Oil and gas firms have got one of the world's leading scientific societies in their pockets, a top geologist says.
Prof Bill McGuire is furious at the links between major fossil fuel companies and the Geological Society.
After more than 40 years as a member, he's resigned from the society – saying it's madness to take cash from firms causing a climate emergency.
The society said geologists were playing a vital role in the transition to the zero carbon economy.
But Prof McGuire told BBC News: "Geologists know more than anyone how suddenly an apparently stable climate can dramatically shift, with massive consequences.
"The society shouldn't be accepting sponsorship from these firms and cosying up to them. It's madness."
He pointed to the corporate sponsors page on the society's website, which features firms like Exxon Mobil that have tried to discredit climate science in the past.
The society gravitates naturally towards fossil fuel firms because they provide many well-paid jobs for geologists.
Prof McGuire said: "The society makes pronouncements on climate change from time to time, but doesn't mention its support from firms that are causing the problem.
"The society conspires with climate change deniers. Hopefully, younger society members will ask what they are doing. There are many geology jobs in engineering or renewables."
Prof McGuire is Emeritus Professor of Geophysical & Climate Hazards at University College London.
In an open letter to the society president, he refers to the sponsors list: "To anyone with even the slightest interest in the sort of world we wish to leave our children and their children, this reads like a tally from hell; a list of some of the biggest despoilers of the surface of our planet, its ecosystems and its atmosphere.
"Even worse, a number of the corporations listed have worked actively to discredit climate science and to undermine efforts to tackle climate change.
"I appreciate that these affiliates are major employers of geologists, but – at a time of climate and ecological emergency – this is quite simply no excuse, nor a justification, for sustaining links with companies that are working against humanity and that put profit before people's lives and livelihoods.
"It truly beggars belief that the society can sign up to a communique on climate change demanding action by government, businesses, public institutions and others – as it did in 2015 – yet continue to cosy up to some of the world's most polluting corporations."
A spokesperson for the society said: "We are not aware of any other members resigning for [Prof McGuire's] reason.
"The Geological Society of London represents geologists from all industries and disciplines, in the UK and abroad.
"We believe the society believes that geologists and geoscience knowledge have a vital role in meeting current targets for reducing emissions and supporting the energy transition."