Prince Charles is in the firing line over an environmental tour on a private jet which is expected to leave a 322-tonne carbon footprint.
The Prince will use his journey to South America next month to focus on environmental sustainability and climate change.
But he and his 14-person entourage - including Camilla, Duchess of Cornwall - will travel on a luxury plane with a VIP lounge, master suite, satellite phone, printer, fax and luxury leather seats, London's Mail on Sunday reported.
The paper quoted Prince Charles' aides as saying the trip, which will cost up to $820,000, would be impossible without a private jet.
And they said he would offset his carbon emissions.
But Labour MP Ian Davidson, a member of the UK Parliament's public accounts committee, said the choice of transport was absurd.
"It would be hard to make this up," he told the Mail on Sunday.
"At a time when the greed of bankers is causing much adverse comment, I would have thought that Prince Charles would have had more sense than to be so financially and ecologically wasteful."
Carbon Managers, a company that specialises in carbon footprint measurement, said the 26,367km trip would emit carbon dioxide equivalent to 322 tonnes.
The Prince's deputy private secretary, Clive Alderton, told the newspaper Charles was extremely mindful of the cost of the trip, and had sought advice from the Government, which said it wanted him to make the journey because of the importance of the issues it would address.
"We looked at all available options of travel but the impracticability of moving around the region on unscheduled flights meant that we had to take the charter option."
In 2007, Prince Charles was criticised for flying first class to the United States to pick up an environmental award.