The Queen is to carbon offset her state visit to the US next month, Buckingham Palace has said.

It is the first time that the monarch has chosen to have a royal tour calculated in terms of its carbon footprint.

A Buckingham Palace spokeswoman said: "Discussions with the Department of Transport have been going on for some time.

"This is indeed the first time that one of the Queen's official state visits will have a carbon offset."

She added: "We intend to offset the cost of this journey to and from the States. The figure is still being calculated."

In January, Prince Charles found himself the subject of criticism for flying to the US to pick up an environmental award.

The Queen and the Duke of Edinburgh will use a BA Boeing 777 to, from and during the trip and be accompanied by an entourage of around 35 people.

In keeping with the green theme, the media have the option of flying back to the UK on the monarch's plane, filling otherwise unused seats, but at the cost of a first class charter ticket.

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