The latest installment in the ciyt's two-month-old crackdown on illegal parking in downtown Washington begins today with a tough, expensive new towing program.

A motorist whose car is towed will have to pay a $50 towing fine in addition to the amount of the ticket incurred before he can retrieve his auto.

The towing operation is the next-to-last stage in a program that began in October when 49 blue-suited civilians took to the streets and began issuing a barrage of parking tickets, about 3,500 a day. Police Chief Burtell Jefferson was one of the thousands of area residents whose autos received tickets from the civilian task force. (He paid up promptly, he said.)

The last stage, to begin Jan. 29, will involve the attachment of metal "boots" to autos that have had a number of parking violations. a boot is a metal device that is attached to a wheel of an auto, preventing it from being moved. After the auto's owner pays all outstanding tickets, the boot will be removed.

The towing program is designed to reduce the number of illegally parked jautos downtown and to force motorists who have ignored parking tickets to pay up. Police officials say the program will bring the city $14 million in additional revenue each year.

Motorists who receive tickets will have to go to the Central Violations Bureau, 451 Indiana Ave. NW, and pay both the towing fee and the ticket, in cash or by check, before going to one of the city's two new impoundment lots to retrieve their cars.

No money will be collected at the impoundment lots, said Thomas Durkins, deputy assistant in the D.C. Transportation Department's parking division.

City officials say the program has worked well so far. The city's revenue from parking tickets was $649,192 higher this December than in December, 1977. The city collected $1.4 million in parking ticket fines last month, said Peter Bergin, chief of the central violations bureau.

Targets of the new towing program are cars blocking fire hydrants, loading zones, bus stops, driveways and alleys, Bergin said.

A motorist whose car is towed can call 724-8561, 724-8562 or 724-8573 to find out which impoundment lot has the car. One lot is in Georgetown, under the Whitehurst Freeway, and the other is in the unopened section of the center Leg Freeway on Third Street between E and F Streets NW.

A third lot, near the Rhode Island Avenue Metro station in Northeast, will be opened Jan. 29, Durkin said.

The transportation department has signed a $1.2 million contract with a private minority firm, Unified Industries Inc., for 25 tow trucks that will remove cars cited by police officers or the civilian ticket writers between the hours of 7 a.m. and 7 p.m.

The Central Violations Bureau will expand its operating hours to open at 7 a.m. and remain open until midnight during weekdays so motorists can pay their fines and get their cars. Central Violations also will be open from 7 a.m. to 3:30 p.m. on Saturdays.

Cars will be towed only on weekdays but the impoundment lots will be open Saturdays.

The new towing program will replace the current one operated by the D.C. Metropolitan Police Department during morning and evening rush hours.

While the police tow an average of 15 to 20 cars daily, DOT officials project they will tow 400 daily.