Two private cable television operators told a D.C. City Council committee last night that they could not build an economically viable cable television system in the District under the requirements proposed by the D.C. Cable TV Design Commission.

One operator pointed to a requirement in the proposed design, which must be approved by the council, that there be only one cable franchise in the District and that the system be built with the capability to serve all residents in the city.

"We conclude that cable television cannot succeed in the District of Columbia if it is forced to serve the entire city," said Terry I. Klein, vice president and general manager of Washington Cable Systems Inc., in prepared testimony before the council's Committee on Public Services and Cable Television.

Washington Cable currently offers cable service to several thousand apartments and homes in parts of Southwest and Northwest Washington, areas the firm chose because of income levels, age of the population and high density of housing, Klein said.

"The cost of installing a cable system to serve the entire District of Columbia is estimated to be in excess of $100 million," Klein said. "This cost is too high to be supported by subscription charges alone--there simply will not be enough subscribers."

The design commission in July proposed a system with at least 60 channels of programming plus two-way communications with institutions such as hospitals and schools and future capability to bank and shop from home.

Robert L. Johnson, president of District Cablevision Inc., which already has indicated its interest in bidding on the system, said the requirement for serving the entire city did not present a problem to him but that a number of other parts of the proposed design do.

These include requirements that the system have two-way capabilities from the beginning of its operation, that all institutions such as hospitals and schools be served, and that the system include several public access studios and mobile vans.

Subscribers simply will not be able to pay the cost of all these services, Johnson said.

"It can mean nothing more than a system which has the highest rates of any major urban cable system in the United States with the provision of fewer services to the basic cable consumer than any other recent cable TV built," Johnson said in prepared testimony.

A third cable-TV operator, Capital City Cable Systems, said it "fully supports the spirit" of the cable commission's proposal, particularly its emphasis on minority participation in the system, but suggested that the council consider dividing the system into several franchises to make it easier for minority-owned companies to bid.

Meanwhile, one member of the design commission, Tayloe Ross, announced her resignation from the commission last night, saying that the public's interests in the cable television design had been ignored.

She accused the commission of "extreme dishonesty" in what she said were strong attempts to keep reports of one of the committees on which she served from being voted on.