The study, conducted by US market research firm Vividence, monitored 2000 credit card customers and prospects as they interacted with ten card Web sites, performing tasks such as checking account balances, reviewing billing statements and paying bills.

Capital One, American Express and Discover Card were found to provide the best overall online experience, but Fleet, MBNA and Bank One customers were the least satisfied.

Overall one in five (21%) customers had difficulty accessing information online, while one in ten (11%) complained about the poor organisation of Web sites. Approximately one in four customers of Fleet, MBNA and Bank One had problems finding or accessing customer support.

The three leading sites also saw an increase in brand perception and customer loyalty. Comparatively, Fleet and MBNA customers were significantly less likely to open a new credit card account or recommend the company to a friend.

Eric Feinberg, financial services consultant at Vividence, says improving the customer's experience online is essential to card companies' bottomline: "The best sites clearly drive brand and customer loyalty, cross-selling opportunities, and card usage. A poor online experience clearly harms perceptions of a company's overall brand and loyalty to that brand."

American Express and Discover Card were the only sites to rate highly among both current and prospective customers. Although Capital One came out top in the survey of its current customers, the site ranked last with prospective customers. Vividence says Capital One's focus on offering just a few card types, as well a lack of online educational information, hurt the company among prospective customers, while American Express, which offers a wide variety of cards, ranked first with prospects.

A third (33%) of participants accessed accounts online at least once a week, with Discover and American Express cardholders being the most active. A growing number of respondents also pay credit card bills via the Internet, with Capital One customers the most consistent online bill payers and Wells Fargo customers the least consistent.

Vividence says customers switch to managing accounts online primarily due to the ease of paying credit card bills and the ability to receive e-statements.