With juvenile shoplifting up 23 percent since last year, the Rockville City Council has endorsed a plan designed to reduce the number of repeat offenders.

Project Intercept, sponsored by the city police department and the Office of Youth Services, offers a rehabilitation program in lieu of criminal prosecution for youths under 18 who have no criminal record and are arrested in the city for shoplifting.

According to Youth Services Director Robert Mateer, the idea has gained support from city merchants who often refrain from prosecuting shoplifters because of the time and paperwork involved. Police say this encourages repeat offenses especially among "kids who are doing it just for kicks."

Under the plan, merchants still have the option of prosecuting a shoplifter. In turn, if the person charged is a first offender, he or she can choose between participation in Project Intercept or going to court.

Those who participate in the program will still be arrested by a city police officer and fingerprinted. Then, as part of Project Intercept, they will tour the county detention center and spend several hours in a cell with an inmate who has been trained by youth services workers to discuss life in prison. They will spend a day in court and ride in a police cruiser. Follow-up counseling will be compulsory.

"We will work on an individualized basis with young people, and we will hopefully impact them enough so there won't be any future criminal activity," said Mateer.

In conjunction with Project Intercept, the council this week endorsed the Metropolitan Washington Board of Trade's ninth annual antishoplifting campaign to be initiated during the winter holiday season when shoplifting is said to increase dramatically.

In other business, the council moved to introduce a Municipal Infractions Ordinance setting fines for residents who violate the city housing maintenance standards, which prohibit overgrowths of weeds on residential property and regulate the numbers of unregistered cars parked on property.

The ordinance is expected to be adopted in early December.

Currently, violators face criminal prosecution, but recent state legislation gave municipalities the authority to set fines in an attempt to "decriminalize the offense," said City Manager Larry Blick.

The council also said it will study a plan by the city Board of Election's Supervisors to eliminate the policy requiring Rockville residents to register separately for city and county elections.

Rockville is the only municipality in Montgomery County that requires separate registration. The board said the single process would double the number of eligible voters. According to board member Kathleen Morrison, only half the Rockville residents who are registered to vote in Montgomery County are also registered to vote in the city. Rockvill has 10,436 registered voters.

It would also prevent confusion by some residents who "assume since they vote in this county, they automatically can vote in this city," Morrison said.

But Mayor William E. Hanna Jr., said he fears that allowing the county to register city voters would "take away the city's uniqueness. Those running for office would lose touch with the voters."

While Hanna did agree a single voter registration was more practical, he said a plan would have to be devised whereby the city would register voters for both city and county elections and not leave the process up to the county.

The mayor and council also agreed to investigate the concerns voiced by members of the city Recreation and Park Advisory Board that Rockville's 26 parks are not being properly maintained.

Board Chairman Leo Leitner said preventive maintenance such as sodding, weeding and minor repairs to equipment is not done because of insufficient funds. The board's current budget is $412,340 for fiscal 1979.

The Advisory Board also asked the council for more police patrols in the city's parks to combat complaints of vandalism, beer drinking and motorized mini-bikes on park land.

Council member Phyllis B. Fordham, who remarked that "nothing makes a city look shabbier than an unkept park," encouraged other council members to look into increasing the park budget.