D.C. People's Counsel Brian Lederer, who represents the public in utility rate hearings, warned last night that telephone service in the District could become prohibitively expensive and urged residents to oppose a plan by the telephone company to charge for some local calls as if they were long distance.

"The most important ingredient is having clear public participation" against the so-called "optional measured service" (OMS) included in the $82 million rate increase sought by Chesapeake & Potomac Telephone Co., Lederer said.

Lederer was among a group of about 30 Advisory Neighborhood Commission members and citizen activists--representing six of the city's eight wards--who met last night at the Calvary Baptist Church in downtown Washington to plan a campaign against the C&P proposal.

"This is a thriving, healthy business; what is at stake is just a question of greed," said Mark Plotkin, a Ward 3 ANC member who helped organize last night's meeting. "We are under attack."

Plotkin said the consumer groups are circulating petitions opposing OMS and are recruiting neighborhood and small business organizations to testify against the C&P proposals. A similar effort helped defeat OMS last year.

Since then, C&P has conducted a massive radio, TV and newspaper advertising campaign to promote OMS as a money-saving alternative for persons who rarely use their phones. In place of a basic monthly service, telephone users would pay for each call based on the time of day, distance involved and duration of a call.

Opponents contend such a service would force users to limit their use of phones for such routine inquires as calling government agencies and politcal organizing. In addition, users would have to keep meticulous records to contest charges.

The Public Service Commission has scheduled public hearings on the proposal for later this month and will hold additional hearings in the fall. A decision on the C&P request could be as much as a year away.

Under the company's rate request, basic telephone service in the District could be increased by 224 percent from $4.51 a month for unlimited service to $14.59.

Installation fees could rise from $9 to $72 and repair service in private homes from a maximum of $9 to $21 for the first 15 minutes of service and $11 for each additional quarter hour.