Environmental organization Greenpeace has protested in an open letter to the Attica Natural Gas Supply Company (EPA-Attica) that a number of claims in a recent advertising leaflet are untrue and misleading. In particular, Greenpeace disputes the claim that gas is an environmentally friendly type of energy, saying it may be cleaner than oil and lignite but still makes a large contribution to the greenhouse effect. Further, it argues that sunlight-based and biomass systems as well as heat pumps are cleaner alternatives for heating requirements than natural gas, which is not “a modern form of energy” as claimed. Finally, Greenpeace contradicts the assertion that natural gas supplies are infinite and urges the company to withdraw or amend the leaflet in question, otherwise it may resort to legal action.