Prince Charles has been accused of hypocrisy for planning a 7,000-mile round trip to the US to pick up an environmental award later this month.
Prince Charles is accused of 'green hypocrisy'
The prince, accompanied by the Duchess of Cornwall and 18 officials, will fly to the US to collect the Global Environmental Citizen Prize.
Environmental campaigners said he should accept the award via video link.
Clarence House said the award ceremony was part of a two-day visit which would highlight environmental issues.
These included conservation, urban redevelopment and youth regeneration, a spokeswoman said.
She insisted the taxpayer-funded £116,000 trip would go ahead as planned, adding: "They are going to the US at the request of the Foreign Office."
Prince Charles will collect the Global Environmental Citizen Prize from former winner Al Gore during visits to New York and Philadelphia on 27 and 28 January.
The highlight will be the Harvard Medical Centre award ceremony attended by Mr Gore and Hollywood star Meryl Streep.
After Prince Charles was invited to pick up the award, the Foreign Office built a programme around the ceremony.
The cost of 14 first-class and six club-class return tickets to the US, on scheduled rather than charter flights, will cost the taxpayer £116,000.
This has led one member of the Commons' public accounts committee to call for an investigation into the cost of the trip by public spending watchdog, the National Audit Office (NAO).
NAO reports are scrutinised by the committee.
Labour MP Ian Davidson said: "[Prince Charles] seems to be travelling yet again on an international flight to collect a green award and padding out his programme with other events to justify the expense and extravagance of another foreign journey.
"This does not sit well with the green image that the prince is trying to project."
Green campaigners have also criticised the Prince's trip.
Joss Garman, spokesman for climate change action group Plane Stupid, said: "Flying to an environmental award ceremony is a bit like turning up to an Oxfam award ceremony in a stretch limo.
"Prince Charles may as well be picking up an award for green hypocrisy, especially since he could have used this to highlight the seriousness of climate change by accepting the award via video link up."
He added: "Flying is the single most polluting way in which you can travel."
Last month Prince Charles announced plans to make his household's travel plans more eco-friendly.
And later this year, he plans to publish details of his own carbon footprint in his annual accounts as well as targets for reducing his household's carbon emissions.