The Prince George's County Council voted unanimously yesterday to establish a county drug analysis laboratory, despite the objections of County Executive Parris Glendening, who had said the project would cost too much.

The council also approved purchase of the county's cable television franchise that serves the northern portion of the county by a group of investors headed by former county executive Winfield M. Kelly Jr.

The drug analysis laboratory, which will analyze drugs seized in police arrests, will cost $262,780 to build and staff, according to figures supplied to the council by the police department.

The Maryland State Police laboratory in Pikesville now analyzes drugs for county cases. But local law enforcement authorities, including State's Attorney Arthur A. Marshall, have complained that the backlog has hindered prosecution efforts.

"A good 50 percent of all our drug cases have been delayed, if not more," Assistant State's Attorney Michael P. Whalen said.

Last year, Prince George's County prosecutors also reduced many drug charges from felonies to misdemeanors in order to ease the drug-enforcement caseload.

Yesterday, Marshall told the council that the 1,100-case backlog is "drastic" and adversely affects the county's efforts to curb a growing problem with the hallucinatory drug phencyclidine, known as PCP.

The state police laboratory is "not physically able to handle this many cases, regardless of what some judges say," Marshall said, noting that Prince George's sends 300 cases a month to Pikesville for analysis.

Howard W. Stone Jr., Glendening's liaison with the council, said Glendening will not veto the bill.

But, he added, the county already had devised a solution to the backlog problem that included the hiring of new chemists at the state laboratory and making plans for such a facility at the vacant Kent Junior High School.

Also yesterday, the council approved a resolution that will allow a group of investors headed by Kelly to purchase the Storer Cable television franchise that services the northern portion of Prince George's County.

Negotiations on the $50 million sale of the 50,000-subscriber system have been under way since November 1983 between Storer Communications of Maryland Inc. and the group headed by Kelly, who helped negotiate Storer's franchises for the county.

Kelly said now that he has gained council approval, he expects the deal to be completed next month. The sale will also include smaller systems in Leesburg and Fort Belvoir, Va.

Storer Communications Inc., a Miami-based firm that operates cable systems in 18 states and owns several television stations, has in recent weeks been the target of a hostile takeover bid by a group of dissident shareholders.

Kelly said yesterday that he has hurried conclusion of the sale because of the uncertainty surrounding the company's future.

"There was some concern that if a new management took over that our contract [of sale] likely would not be renewed," Kelly said.

That contract expires in May.

Officials said yesterday that they do not anticipate that subscriber rates will increase as a result of the transfer of ownership.