Carbon offsetting allows air travellers to balance out the effect of their flight on the environment by contributing to green projects such as tree planting or the retirement of carbon credits for polluting industries. But recent investigations into firms offering the schemes have rendered the business controversial.

The airline's marketing manager Michael O'Callarain declined to say when the service will be introduced.

"We're looking at a carbon offsetting programme and we will be announcing it shortly. We're still looking at the mechanism we will use and there's no final decision yet, " he said.

O Callarain said, however, that Aer Arann's website would be "an obvious channel" through which to offer the service because 85% of the airline's bookings came through it.

He added that the airline did not expect carbon offsetting to become a significant source of income, particularly as the turboprop aircraft it employed uses less fuel than jets. "We're not looking at it as a revenue stream. We're looking at it as a customer service."

Ireland's two other major airlines, Aer Lingus and Ryanair, have both ruled out offering carbon offsetting to their passengers. A spokeswoman for Aer Lingus said that although the airline was monitoring the situation, it had no current plans to introduce such a service. Meanwhile, Ryanair said it had no plans to ever introduce carbon offsetting, arguing that aviation accounted for just 2% of total emissions.

Some carbon offsetting companies have been accused of overcharging customers. British low-cost airline EasyJet accusing them of being "snake oil salesmen". The company revealed last week that it had been forced to delay the launch of its offsetting scheme due to the high administration fees sought by the firms it approached. It now plans to sell carbon offsets directly to its customers.