Piers Corbyn, physicist and founder of long-range forecasting group Weatheraction, told a meeting of Charity 2000, a networking group that brings together senior people from charities with leading figures from other sectors, that carbon dioxide had no net influence on world temperatures.
Corbyn, a climate change sceptic, claims the theory of emission reductions has no scientific basis.
"Any investment based on saving the planet from carbon dioxide should be ignored absolutely," he said. "Tidal power has definite potential. Another good investment would be businesses that will help to combat chemical pollution."
Responding after the event, Sam Collin, adviser to socially responsible investment initiative the Eiris/UKSIF Charity Project, said: "Charities can invest in an environmentally responsible way by, for example, avoiding companies that are not addressing the challenges of climate change."