The oldest profession is one of the few sectors that is generally immune to global economic problems. But high oil prices are another thing — especially when many of your regular clients are truckers.

According to the Nevada Brothel Owners' Association, revenue for houses of ill-repute has dropped by 20 to 45 per cent since the energy crunch began — the worst economic crisis in prostitution in almost half a century.

“Old George or Jimmy out there, he's got to take care of Momma and the groceries first, and he's got to take care of fuel costs, and he's got other expenses, and he may not have much left over for having a good time,” George Flint, a director of the association, said.

At the Stardust Ranch in eastern Nevada, so many girls have been made redundant that only two are still working there, despite the management offering incentives such as free showers, overnight parking and coffee.

At other brothels in the Nevada desert - where it has been legal to sell sex at licensed establishments since the silver mining boom of the 1800s - petrol discount schemes, similar to those offered by Chrysler to customers when they buy a 4x4 Jeep, are being introduced. Some have abandoned the financial negotiations that take place between customers and girls and are offering flat-rate, no-haggle services, advertised online. At the Shady Lady Ranch, for example, a 40-minute session is being promoted for the discount price of $175 (£90). Next month, customers will receive a $50 petrol voucher if they spend at least $300, or a $100 voucher if they spend $500.

Truckers are the ideal customers for brothels. Bored, a long way from home and with nothing much to spend their money on while on the road, they are often tempted by the prospect of the intimate company of women.

On the website for the Wild Horse Adult Resort and Spa, the truck-friendly five-acre car park, with 24-hour security, is given almost as much advertising space as the services.

Fuel bills for truckers have risen by two thirds in the past year — diesel has gone from an average of $2.80 per gallon to $4.69 per gallon. It is no help that many brothels are several hours' drive outside metropolitan areas because of licensing restrictions.

Politicians have tried to help. Last July a ban on advertising was lifted, allowing brothels to put up billboards in cities such as Las Vegas, where prostitution is illegal. President Bush's tax refund cheques have also helped. At the Moonlite Bunny Ranch, which featured in a recent HBO reality TV series, the first 100 customers who showed up with their tax refunds were offered special deals.

“You bring your $600 cheque in, and we give you the $1,200 George Bush party: three girls and a bottle of champagne,” Dennis Hof, the owner, promised.

Because of the promotion, business at the establishment is reportedly up 20 per cent this year.

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