There will be glitz, glamour and painfully thin models but the London Fashion Week is set to be shunned by the biggest US retailers in protest at "exorbitant" prices.

Buyers from flagship department stores such as Saks Fifth Avenue and Barneys are planning to make Paris their sole European fashion destination as the weak dollar and transatlantic economic worries force them into tough choices.

Julie Gilhart, fashion director of Barneys, one of the US champions of British designers, said she would not be making it to the London catwalks for the first time in 20 years and that although UK designers could still make sales in Paris, their pieces would have to be "really special, really different and really worth it".

Saks Fifth Avenue, which has also promoted designers from the UK, will unusually not be sending a member of its New York fashion team. "The product is very, very expensive, so it has got to be very special, and that's a very difficult scenario for a new brand," said Ron Frasch, president of the chain.

"It's a real struggle for small businesses, which most of the London businesses are," he said. "At a time like this it's very difficult to elbow your way in. The young designers will never be successful."

British designers are considered expensive, partly because their smaller production runs do not allow big economies of scale. But the weakness of the dollar has made their pieces even less competitive at a time of economic pressure in the US.

"I think the current economic climate has affected things," acknowledged the British Fashion Council, which promotes the event.

One New York retailer, who asked to remain anonymous, said: "The London designer prices are just exorbitant. You can buy a piece by Balenciaga [the French label that is hot in world fashion] for a certain price, and a piece by Giles [Deacon, the less well-known British designer] for the same price, and when you put them on the floor, which do you think will move faster? That's the problem."

Ann Stordahl, executive vice-president of Neiman Marcus, said: "Some designers have been able to absorb some of the currency conversion rate of the retailers to keep the relationship, but it's generally the big brands who can do that."