Apartment managers and owners of commercial propert in Arlington County who have hired private towing companies to cruise their parking lots and automatically tow away cars parked without permission have been told by Commonwealth's Attorney William S. Burroughs that the practice is illegal.

Burroughs said in a letter that based on his interpretations of state law, decisions to tow cars must be made by a property owner or his representative on a "car-by-car basis" rather than in a "blanket manner," as has often been done in Arlington.

Copies of Burroughs' letter were sent to police department officials, the Chamber of Commerce, the county's estimated 30 licensed tow truck operators and the Northern Virginia APartment Owners Association, the prosecutor said.

Towed cars must be taken to licensed garages in Arlington, Burrough said, and the parking lot owners, not representatives of the towing companies, must notify police whenever a car is towed. Burroughs said that most Arlington companies charge $25 to $35 for a tow.

Police Capt. William Stover said that most of the complaints his department received over the last several months concerned towing in large apartment complexes and business parking lot in Rosslyn and Crystal City. Stover said most of the towing occurred at nights and on weekends.

"What would happen is that sometimes cars would be towed and people would call the police department, who didn't know anything about it," said Chamber of Commerce president Norman C. Worthington. "Sometimes it would take a guy half a day to find his car."

County Manager Vernon Ford said that he has heard numerous complaints about towing practices at the Arlington Towers apartment complex in Rosslyn.

"One man got a visitor's permit to park in the lot there which expired at midnight," Ford said. "He came out a half hour late and found his car gone."

Harry Scanlan, assistant manger at Arlington Towers, said the complex has for several years contracted with a 24-hour Arlington towing service to patrol the parking lots and tow away any cars parked in violation of posted rules. He declined to name the towing firm.

"Our policy is that a car in violation is towed, but the company notifies the police," Scanlan said. He estimated that about 10 cars per week are towed from Arlington Towes. "We just got the letter today and we're reviewing it now for possible changes in our policy," he said.

In Prince George's County a law designed to prevent towing abuses is scheduled to go into effect March 1. Observers contend that some tow truck operators cruise nightly through apartment parking lots towing away cars including some that are parked legally.

The new law requires that the tow truck operator secure written permission from a resident or property manager before towing away cars.