Charles Schwab Corp's customer satisfaction topped that of rival Fidelity Investments for the first time ever in 2010, according to a new annual online brokerage study released by the American Customer Satisfaction Index on Tuesday.

The San Francisco-based online broker reported the highest customer satisfaction among the four major U.S. online brokerages, breaking a deadlock from a year earlier with Boston-based Fidelity.

The ACSI's report ranks satisfaction on a 100-point scale. In the most recent report, Schwab's customer satisfaction rose to 80 from 79 a year prior, while Fidelity's dropped one point to 78.

The range of customer satisfaction scores for the four online brokerages also narrowed to the tightest margin since the study was first conducted in 2000.

They're all coming together in terms of how they operate, which is ultimately a positive for the consumer, said Larry Freed, CEO of ForeSee Results, which conducted the survey for ACSI.

Freed said the narrow gap will make it more difficult for brokerages to poach clients, and will heighten competition for new customers.

TD Ameritrade Holding Corp posted an ACSI score of 77.

E*Trade Financial Corp posted a 76 satisfaction score -- the lowest among the four rivals -- but the figure was a 3 percent increase, the largest among the four major online brokerages.

The study was conducted in the 2010 fourth quarter and surveyed 1,250 online brokerage customers.

(Reporting by Joe Rauch; Editing by Phil Berlowitz)