Prince Charles is being accused of hypocrisy after planning to fly more than 11,000 kilometres with a staff of 20 people on a jumbo jet to accept an environmental award.

Charles, who has spoken publicly on the threat of climate change, will receive a Global Environmental Citizen prize from Harvard Medical School's Centre for Health and the Global Environment later this month.

Former American vice-president Al Gore, who recently made a documentary about climate change, will present the award at a glitzy ceremony attended by actress Meryl Streep.

Environmentalists say he could accept the award via video link, but the prince's office said he is making the two-day visit to Philadelphia and New York at the request of the Foreign Office to promote climate change as a key priority of the British government.

A spokesperson for the environmental group Plane Stupid accused Prince Charles of "green hypocrisy."

"Flying to an environmental award ceremony is a bit like turning up to an Oxfam award ceremony in a stretch limo," said Joss Garman.

A representative of Britain's Green party said he was "disappointed" in the prince.

"I am disappointed to see that— much like Tony Blair— his recognition of the threat posed by climate change does not extend to toning down his personal flying habits. Why can't he set a genuine example and accept the award by video link instead?" said Sian Berry.

Charles and his wife Camilla willbein the U.S.Jan. 27-28.