Fears are mounting that prices of artwork could halve as rich investors show signs of reining in their spending.

Lehman Brothers CEO Dick Fuld sold several pieces of art in November. Last Wednesday a separate auction saw 11 lots unsold

Hiscox, the largest specialist insurer of fine art in Europe, said the market traditionally lags a recession by a year to 18 months but the early indications are that it is becoming increasingly challenging. Charles Dupplin, chairman of Hiscox's art and private client division, said prices are holding up reasonably well but at a Russian art sales at Christie's on Wednesday, half of the 22 lots were unsold.

"That is quite a lot. You would expect to have 25pc unsold but that means there is less liquidity in the market. No matter how rich you are, probably your confidence has dropped. In 1991, prices fell about 50pc for Impressionist art. There is no reason to believe that history might not repeat itself."

Mr Dupplin described the auction house's sale as a key indicator as recently Russians have "provided a lot of the money spent on contemporary art". He noted at the Christie's sale on Wednesday, notable works which were unsold included Alexandre Lacovleff's "Nudes Bathing" which had an estimate of £1.2m to £1.6m and Konstantin Somov's "The Boxer", valued at between £600,000 to £900,000.

He added at Sotheby's Russian art evening sale on Monday, 23 of the 55 lots went unsold and several works tipped to reach top prices didn't sell. They included Ivan Konstantinovich Aivazovsky's "View of Constantinople and the Bosphorus" which was estimated to fetch £2.5m to £3m, although bidding stopped at £2.4m.

Signs that the art market is starting to feel the impact of the credit crisis come as a range of elitist "hobbies" have been hit. Recently yacht prices have dropped and the price of yearlings in the bloodstock market have tumbled by up to 50pc.

Aon, the world's largest insurance broker, said it has concerns that its clients will not be so active in increasing their collections in the near future. Charles Hamilton-Stubber, director of its private risk management team, said: "We have not yet seen a rush to the telephones to decrease the value of insured art but everybody is on watch because everything is so volatile at present.