One of Greenpeace's most senior executives commutes 400km each way to work by plane, the environmental group has admitted.
Pascal Husting, the programme director at Greenpeace International, said he began "commuting between Luxembourg and Amsterdam" when he took the job in 2012 and made the round trip about twice a month.
The flights, costing 250 ($390) return, are paid by Greenpeace, even though it campaigns to cut air travel, arguing the growth in flying "is ruining our chances of stopping dangerous climate change".
One volunteer described the arrangement as "almost unbelievable". Another was going to cancel their donation after a series of disclosures about financial mismanagement in documents leaked to the Guardian newspaper.
Greenpeace was forced to apologise for a "serious error of judgment" last week, after it emerged it had lost 3.75 million of public donations when a member of staff tried unauthorised currency dealing. KLM airline said each round trip Husting made would generate 142kg of carbon dioxide emissions - a carbon footprint equivalent over two years to consuming 17 barrels of oil, according to the US Environmental Protection Agency.
Husting said while he would "rather not take" the journey, it would be "a 12-hour round-trip by train".
"I spend half my life on Skype and video conference calls," he said. "But as a senior manager, the people who work in my team sometimes need to meet me in the flesh."
From September, he would be making the trip only once a month and by train, because his team's restructuring would be coming to an end "and my kids will be a little older".
John Saven, the head of Greenpeace in Britain, wrote in his blog: "Well, it's a really tough one. Was it the right decision to allow him to use air travel to try to balance his job with the needs of his family for a while?
"Honesty and integrity to the values at the heart of the good you're trying to do in the world cannot be allowed to slip away. For what it's worth, I don't think we've crossed that line."
Richard Lancaster, who said he'd been involved with Greenpeace since the 1980s, responded: "I volunteer with Greenpeace but work in the commercial world and if I took a job in another country I'd expect to move to where the job is ... I find Pascal's travel arrangements almost unbelievable." Another supporter wrote: "So disappointed. Hardly had 2 pennies to rub together but have supported GP for 35+ years. Cancelling [direct debit]."
Greenpeace has campaigned to curb air travel and end "needless" domestic flights. In a briefing on aviation the group said: "In terms of damage to the climate, flying is 10 times worse than taking the train."