Branson fails to read the small print as he signs contract about dieting

So when Sir Richard Branson and Boeing chairman Jim McNerney signed a £4billion deal for a fleet of lighter, more fuel-efficient aircraft, it was hailed as a sign of the industry's commitment to the environment.

Sir Richard Branson - who is classified as overweight - mistakenly signed a contract about dieting with Boeing chief Jim McNerney (right)

What few people noticed was that the deal between Virgin Atlantic and Boeing included a bizarre clause pledging that their respective chairmen would each lose a stone in weight to help reduce their carbon footprints when flying.

But what may have started as a joke by the lawyers has been dubbed "a cheap gimmick" by green campaigners.

The pledge was written into a contract signed by the pair agreeing the sale of up to 43 Boeing 787 "Dreamliners".

Both Branson and Boeing boss Jim McNerney ignored the small print

The clause reads: "The parties hereby agree that each of the signatories will lose at least one stone in weight within the next four years in order to reduce carbon dioxide emissions by over 36lb on the delivery flight."

Branson, 57, is 6 feet tall, weighs 14 stone 9lb and has a BMI of 27.4 - classed as overweight by the National Institute of Health.

His communications director Paul Charles said staff wrote the clause into the agreement as a joke to see if their chairmen would read the small print.

"Clearly, neither of them reads contracts properly before they sign them," he said. "They had no idea they had agreed to lose weight until after their signatures were down on the dotted line. They thought it was very funny."

The 787, which will enter service next year, is made from carbon fibre rather than aluminium, meaning it is much lighter and burns less fuel.

Mr Charles said: "We are doing our bit to tackle carbon emissions, but losing weight was an additional element thrown in for added effect.

"If you are carrying lighter people in the plane, you need even less fuel. Perhaps the Government should consider adopting it as a way to combat obesity and climate change in one go."

A spokesman for Mr McNerney said he too would be taking part in the weight-loss challenge but was unable to provide the Boeing chairman's vital statistics.

Green campaigners failed to see the funny side. Joss Garman of anti-flying group Plane Stupid said: "Branson's fleet produces 7.4 million tonnes of CO2 each year. He and McNerney are both very carbon-obese men, but they seem to have mistaken a low-carb diet for a low carbon one.

"It's the flying that's the problem, Richard, not the frying."

A spokeswoman for Greenpeace accused the pair of "making a mockery out of the dangers of climate change" and Friends Of The Earth aviation campaigner Richard Dyer called it a "cheap gimmick". He said: "I would much rather know how he was planning to cut carbon emissions from his aircraft than fat from his waistline."