In a "sneak preview" of possible changes in Federal Communications Commission Policy toward television networks, FCC Chairman Charles Ferris yesterday suggested that more networks are needed.

"There is no magic in the number three," Ferris said. "The commission should not inhibit the development of additional television networks."

Rejecting contentions that the FCC ought to break up the networks to promote greater diversity of television program, Ferris said that what is needed is not fewer networks but more of them.

Ferris' call for additional outlets for television programming was sounded in a speech prepared for a communications law symposium at the University of California at Los Angeles, in the backyard of the Hollywood television industry.

The FCC's staff is in the midst of a major "network inquiry" and is expected to produce by this summer a preliminary report recomm ending FCC actions to answer critics of network programming.

The critics, Ferris noted, complain that television networks cater only to mass market tastes, produce "homogenized programs, "dwell excessively on themes of sex and violence... deny reative talent access to the American viewing public... and...

"Prevent local television stations from programming for local audiences.

"The complaints about the existing television system in our nation have a base of leitimate concern," the nation's top broadcasting regulator said.

But "the real problem we face concerning networks today is not that they exist, but that there are so few of them," Ferris said.

Networks can spread the high cost of news, sports and entertainment programming among many stations, he said, creating a broader range of higher quality viewing.

The economics of the network system, he acknowledged, can make it virtually impossible for any program that does not appeal to a mass audience to get on the air.

Rather than dictate the content of programs, Ferris said, the FCC ought to concentrate on the structure of the television industry.

"We should seek to assure that networks do not abuse their dominant positions. We should prevent the exercise by networks of powers to limit station or producer opetions."

Ferris said his remarks were not meant to detail the FCC's emerging policy but rather to indicate the direction in which he, as chairman, sees the agency moving.

He said the FCC's network inquiry is investigating "a variety of allegedly abusive network-supplier and network-affiliate practices," and will recommend ways to separate television networks and sponsors from the content of programs.

And, he added, the FCC "should seek to foster and maintain conditions in the communications marketplace that will enable edditional networks and alternate forms of networking to emerge."

New networks would not have to be as big as ABC, CBS and NBC to be effective, Ferris said, citing the success of religious and sports network, and the temporary ststems assembled to handle special programs.