Ryanair will introduce a 25 euro cents levy on every seat booked from next week to cover the expected EUR€18 million - EUR€20 million cost of carbon permits it needs this year under a new European Union emissions trading scheme.
Europe's largest budget airline on Monday followed US group Delta Air Lines and Lufthansa in passing costs onto customers.
"We do not agree with it and we do not believe there will be any environmental benefit," a Ryanair spokesman said.
Under plans to tackle climate change, airlines touching down or taking off in the 27-nation European Union must account for their CO2 emissions as part of an expansion of the world's largest carbon market.
Airlines and their associations have objected to the scheme and challenged it in court, saying it further burdened an industry saddled with high fuel prices, fierce competition and national taxes.
Europe's highest court last month backed the scheme, meaning all airlines will have to pay for emissions permits, drawing anger from the United States and China.