(Bloomberg News) Christie's International said there was a surge in demand for contemporary art as an investment, after its sales climbed 9 percent in 2011.

The London-based auction house sold 3.6 billion pounds ($5.7 billion) of art and collectibles last year, a pound- sterling record for the company, it said in an e-mailed release sent last night. Contemporary works -- led by Roy Lichtenstein, Andy Warhol and Mark Rothko -- were the most lucrative category, contributing 735.7 million pounds at public sales, an increase of 22 percent.

Diminished returns from stocks and other financial investments have encouraged wealthy individuals to turn to art, particularly classic contemporary works, as an alternative asset class.

"Investors are entering the market and existing collectors are buying more," Steven Murphy, Christie's chief executive, said in an interview. "The ease with which information and images can be accessed through the Internet is also helping create a fundamental increase in demand."

Equivalent auctions for Impressionist and modern pieces --a powerhouse of record results since the 1980s -- declined 28 percent to 548.6 million pounds, behind Asian art at 552.9 million pounds, which increased 13 percent in 2011.

This is only the second year that contemporary art has topped auctions at Christie's. Catalogs featuring works by artists such as Warhol, Damien Hirst and Jeff Koons generated a record 772 million pounds of sales in 2007.

Lichtenstein's 1961 canvas "I Can See the Whole Room!... And There's Nobody in It!" was the most expensive individual lot at Christie's in 2011, fetching a record $43.2 million in New York on Nov. 8. Paintings by Warhol and Rothko sold for $38.4 million and $33.7 million respectively in May.

Pablo Picasso's 1939 painting, "Femme assise, robe bleue," was the top Impressionist and modern seller at 18 million pounds in London in June.

"I wouldn't attribute trends to one year of sales," Murphy said. "Great works by Picasso and Modigliani emerged from collections in 2010. There's always an ebb and flow of quality appearing at auctions."

Private transactions increased 44 percent to 502 million pounds in 2011. These include an undisclosed amount of sales at Haunch of Venison, a London-based gallery wholly owned by Christie's, which said that 20th-century art and jewelry were the main contributors to the overall total.

Elizabeth Taylor

Christie's 2011 figures were boosted by the five-catalog sale in New York in December of Elizabeth Taylor's collection. All 1,778 lots found buyers, raising a total of $157 million. An inaugural online auction of lower-value items that had belonged to the Oscar-winning actress, who died last year, contributed $9.5 million.

Collectors are still reluctant to buy big-ticket art via the Internet. Just two of the 719 works Christie's sold for more than $1 million in 2011 were bought using online bidding.

New York remains the company's biggest auction center, with 1.2 billion pounds of sales in 2011, 6 percent down on 2010. London, which hosts three series of contemporary-art auctions each year, was up 20 percent to 871.6 million pounds.

Growth in Hong Kong slowed to 11 percent with 519.1 million pounds of transactions. In 2010, auctions in Asia rose 114 percent. China, Hong Kong and Taiwan's share of client registrations from increased just 2 percent last year.

New clients represented 12 percent of the value of Christie's international sales, the auction house said.

Christie's is a private company owned by the French billionaire Francois Pinault. The auction house was bought by Pinault's holding company, Artemis SA, for $1.2 billion in May 1998. Christie's doesn't report revenue or profit, though it gives sale totals twice a year.

Christie's said its policy, in line with U.K. accounting standards, is to convert non-U.K. results using an average exchange rate weighted daily by sales throughout the year. This would make the 2011 total of 3.6 billion pounds come to $5.7 billion. In 2010, it had sales of 3.3 billion pounds.

Sotheby's said that it will release its consolidated total of private and auction sales for 2011 at the end of February. It raised $4.8 billion in 2010.

(Scott Reyburn writes about the art market for Muse, the arts and culture section of Bloomberg News. Opinions expressed are his own.)