The Prince of Wales was still deciding yesterday how to offset the carbon dioxide generated by a two-day visit to the United States - to pick up an award as a leading environmentalist.
In a move called "eco-insanity" by campaigners, the heir to the throne and his wife, the Duchess of Cornwall, flew to Philadelphia yesterday with 12 members of staff, including a hairdresser, a butler and two valets.
Prince Charles will travel to New York tomorrow to receive the Global Environmental Citizen award from former the vice-president Al Gore at a ceremony put on by Harvard Medical School, where millionaires and corporate donors will dine on "sustainable cuisine".
A spokesman for Harvard said the heir to the throne was being recognised for his "outstanding work towards protecting the global environment".
The royal party crossed the Atlantic on a scheduled British Airways flight after booking space in the first class cabin. The price of a first class return to New York's is £6,660. Clarence House insisted that the entourage, which includes a doctor, two private secretaries, two press officers and three people to handle "luggage and logistics", had been cut down to a minimum.
But despite making the 11,000-mile round trip to be lauded as a pioneer on green issues, officials were was unable to say how or when the 20.4 tons of CO2 created by the flights would be offset. Aides insisted that the decision to redeem the CO2 from the aircraft journeys was an important first for the Prince's household.
But The Independent has been told they are still waiting to decide whether to join the Government's scheme to offset official flights or set up a separate royal offsetting scheme. A spokeswoman for Clarence House said: "The flights will be offset but it is yet to be determined under which scheme - the one already operated by the Government or an arrangement of the Royal Household."
The Government confirmed that it was in talks with the Prince's officials over whether to join its offsetting scheme for flights by ministers and officials, announced last year with a budget of £3m.
Royal sources pointed out that the Prince was making the trip at the behest of the Foreign Office and will include a tour of community projects and historic sites. He will travel to New York to receive the award by "private train".
Critics said the visit was nonetheless richly ironic.
The Prince will publish details of his carbon footprint in his annual accounts this summer.
Joss Garman, of campaign group Plane Stupid, said: "If the Prince was serious about dealing with carbon emissions, he wouldn't be flying all that way to receive an award for environmentalism in the first place. It is a form of eco-insanity to expend so much energy for such meagre reasons. Offsetting should be an action of last resort because it is a false economy to believe it negates the CO2 caused by flying."
Campaigners added they were also uncertain about the significance of the award from Harvard's Center for Human Health and Global Environment, whose sponsors include BP, which was criticised in America last week for its safety record following a fatal explosion at a refinery in Texas two years ago.
Those attending the ceremony tomorrow evening in Manhattan can at least be assured the food they eat will be environmentally sound. Harvard said it had recruited three chefs to create a menu based on local seasonal produce but declined to give details of the menu. Last year, guests dined on dishes included corn succotash soup laced with huitlacoche, a fungus that grows naturally on wheat and is considered a delicacy in Mexico.