Fairfax County Board Chairman John F. Herrity yesterday branded a six-month citizen commission report on cable television as a "piece of garbage" and accused the panel of trying to stall the county's prolonged cable contract process.

"This doesn't say anything we didn't know before," groused Herrity, who has complained repeatedly about county studies and public hearings that have pushed the expected completion date of a county cable system back to 1988. "It's about time that we just stopped fiddling around."

But other members of the board rejected Herrity's complaints about county studies and public hearings that have pushed the expected completion date of the cable system ahead to 1988. Instead, they approved further study of the commission's suggestion that the county get more deeply involved in regulating cable than had previously been contemplated.

"I feel that we will have a better product for citizens as a result of the commission's work," said Supervisor Martha V. Pennino (D -- Centreville), before the board's 8-0 vote. Herrity voted with the majority, having failed to muster any suppoet for a motion to ignore the report altogether.

Yesterday's decision probably will add a few more months to what has already been a three-year-long struggle to bring cable TV to Fairfax County. Although Herrity says he has received numerous complaints from constituents who want to watch first run movies at home, others on the board maintained that federal deregulation of the infant cable industry requires that the county proceed with caution.

Some board members have said they are particularly wary of awarding the franchise too quickly in light of cable problems in neighboring Arlington, where local officials have received numerous consumer complaints about Arlington Telecommunications Corp. (ARTEC).

ARTEC became the area's first franchised cable company in 1973 after it assured the county it would provide channels for public use and the equipment necessary to run them. Eight years later, however, county officials say many of ARTEC's promises have not been kept and ARTEC is almost $6 million in debt.

Stan Slater, chairman of the Consumer Protection Commission, yesterday defended his panel's report as "substantial" and "very responsive to the questions the board has asked."

The report urges the board to become more deeply involved in cable regulation and calls for greater citizen involvement in the process.

Included are recommendations that the county:

Protect the privacy of cable subscribers by restricting the collection and use of personal data through the cable television system. Without such restrictions, the report warned, a cable TV system could be used to intercept and distribute information on an individual's banking transactions, home security, religious preferences and viewing habits without his knowledge or consent;

Discourage, through economic sanctions, the industry practice of granting cheap cable stock to prominent local citizens in exchange for their help in winning lucrative franchise contracts;

Create a nonprofit organization to manage the county's public use, or so-called community access, channels; and

Create a cable television advisory commission to advise the board of supervisors on cable TV matters.

The commission also rejected suggestions by some supervisors that the county could make a substantial profit by owning its own cable system, concluding that Fairfax lacks the legal authority to embark on such a venture.

County cable administrator William Rossi said yesterday that construction of the cable system would probably not begin until 1983 at the earliest, with completion expected five years later.