Resources companies are growing increasingly nervous about fossil fuel divestment as the numbers of investors that cut or reduced their exposure to oil, gas and coal surged in the lead up to critical climate talks in Paris, according to the head of one of America's best-known philanthropic foundations.

Green investment campaigners 350.org and Divest-Invest on Wednesday claimed more than 100 institutions representing $US800 billion under management divested at least some of their fossil interests in the 10 weeks ahead of the United Nations climate change conference in the French capital.