The Montgomery County Council yesterday approved a sweeping cable television bill giving the council broad new regulatory powers over cable television and making Montgomery the first known local jurisdiction in the nation to submit a cable company to a county antitrust law.

The measure, passed by a 5-to-2 vote after two day-long debates, could jeopardize the county's franchise agreement with Tribune-United of Montgomery County. The firm's lawyer had said the contract might have to be renegotiated and the rates for cable service increased if the proposal was approved.

The antitrust section--which passed over the heated objections of County Executive Charles W. Gilchrist and a representative of the cable firm--could make Tribune-United subject to criminal prosecution by the state's attorney if the firm engages in anticompetitive behavior. The measure also requires the firm to submit, on request, a "competitive impact statement" detailing how its actions may affect competition in the county.

Council President David L. Scull said Montgomery needed its own antitrust law in case federal or state antitrust statutes did not apply. An example cited by one council member: If Tribune-United opened one of its many television channels to a burglar alarm company offering home protection via the cable wires, then the cable firm would have to make the same offer to all burglar alarm companies or be subject to criminal prosecution or civil suits.

Gilchrist aide Edmond F. Rovner said later that he didn't know if Gilchrist would sign or veto the bill. Five votes--the number the bill received yesterday--are needed to override a veto.

Supporters of the measure conceded that local governments usually never get involved in deciding complex antitrust questions. "The fact is, we're different," said council vice president Esther P. Gelman. She added, "Whatever we've done to overprotect the public interest can only be to our credit."

Council member Neal Potter, usually a Gilchrist ally, switched to the Scull majority to become the crucial fifth vote to pass the bill. Despite his vote, Potter said he still worried that the new regulations might create unneeded burdens for Tribune-United. "Certainly harm can result from undo suspicion or harassment," Potter said.

The final vote came after hours of bickering between the council members supporting the bill and the Gilchrist aides and the cable representative opposing it.

During one such exchange, Gilchrist cable project manager John Hansman, normally soft-spoken, slammed the table top and later retreated to stand in the back of the council chambers, saying he had lost his patience.

Fern Krauss, the cable company representative, sat in on one session, at times angrily interrupting backers Scull and Gelman in her opposition to the bill, waving her arms and slapping her forehead. At one point she drew a polite rebuke from Gelman.

Council member Rose Crenca, who opposed the bill, questioned whether it "is just a nuisance bill to punish the franchisee who won, or is there another contractor waiting in the wings?"

Cable representative Krauss said afterward the firm would have no official reaction until its lawyers could review the final version of the bill.