The move is the realisation of a five-year dream for Sir Richard Branson, the airline’s chairman, who has been keen to give passengers a chance to get “closer together” on long-haul trips.

His supporters point out that amorous couples will no longer have to sneak off to the plane’s lavatories and risk being caught in a compromising position.

Critics, however, believe that Virgin is overstepping the boundaries of taste and decency and could end up angering more passengers than it pleases.

“This is unnecessary and unfortunate,” said Ann Widdecombe, the former shadow home secretary who is about to embark on a career as an agony aunt for the BBC.

“There’s an immense issue of public decency here because there are other passengers who will not wish to see or hear such things.”

Travellers can take advantage of the double beds — which can be requested at the check-in — on three Boeing 747s that fly transatlantic routes out of Heathrow.

Virgin aims to offer the option to couples on another three planes, possibly including services to South Africa, by the end of the year.

The airline has fitted four double beds in the central section of its Upper Class suites. Normally they are adjacent seats divided by a partition. But at night the partition can be removed, the seats converted into flat-beds and the space in between filled with a mattress.

Prices start at around £2,000 per person on a return trip to New York and there are already rumours that Virgin is considering installing condom machines on its aircraft.

But before passion takes over completely, couples should be warned: while they are shielded by screens from passengers to the front and back, they could be seen by people walking down the aisles.

This weekend Branson managed to promote his new product without explicitly mentioning sex. “We have a lot of honeymoon couples who fly on Virgin, and a lot of couples who have been together for many years. There is no reason why they shouldn’t cuddle up on board like they would at home,” he said.

However, the Virgin boss has not been so euphemistic in the past. When he first floated the double bed idea in 1999, he said: “The legitimate mile-high club is finally aboard . . . You can do it on cruise ships, you can do it at home, so why shouldn’t you be able to have relationships on planes?”

A spokesman for the airline hinted yesterday that cabin crew who caught couples having sex would only intervene if they received complaints from other travellers. “We want passengers to enjoy themselves on the flight — as long as they are discreet and don’t upset other passengers,” she said.

The mile-high club is almost as old as the history of flight. Its founding members are thought to have been Lawrence Sperry, a dare-devil American pilot, and Mrs Waldo Polk, a wealthy socialite, who hit the heights of passion in a biplane over New York state in 1916. They crash-landed when Sperry became too distracted to steer.

Celebrity members of the mile-high club include Oliver Reed, the late actor, and Pamela Anderson, the glamour model.

In October 1999, David Machin, a manager for a greetings card firm, and Amanda Holt, a car sales manager, faced public embarrassment after they got drunk on an American Airlines flight from Dallas, Texas, to Manchester and allegedly engaged in sex acts.

The couple, who were strangers before the flight and were both married, were arrested on arrival and were later fined a total of £2,250 for being drunk on board a plane.

Further charges of outraging public decency were dropped. But both Machin and Holt, who was seen by passengers stripped to her underwear, were sacked by their employers.

In 2001, a couple flying in Club Class on a British Airways flight from Phoenix, Arizona, to Gatwick, received a ticking off after fellow travellers complained about their noisy antics under a blanket.

In another incident in the same year, BA cabin crew had to unscrew a lavatory door after a couple locked themselves in for an hour.

BA said there are one or two couples caught each year trying to join the mile-high club on its flights. “But these are just the cases we know about,” said a spokesman. “Who knows what other people do?”

BA has no plans to follow Virgin’s lead. “While it might be very interesting for the couples concerned, you probably wouldn’t be having quite so much fun if you were in the next seat,” said the spokesman.

Brian Donohoe, a Labour member of the Commons transport committee, said: “I can’t wait for Sir Richard to offer me and my wife a flight with these double beds — but just for a good-night cuddle,” he said. “What else would I possibly be thinking about?”

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