About 170 inmates at the District's Lorton Reformatory staged a work stoppage yesterday to protest conditions, including the increased use of shakedowns and a general tightening of security measures.

The inmates remained in their cells in the prison's maximum security facility and issued a list of 14 grievances and demands, according to a spokesman for the D.C. Department of Corrections. Prison officials warned the inmates that they would lose their visiting privileges unless they returned to their jobs by noon today. "We don't negotiate," said Leroy B. Anderson, the department spokesman.

Bernard Demczuk, an official of the American Federation of Government Employees, which represents corrections officers at Lorton, said there were no reports of violence stemming from the demonstration. "It's a peaceful sitdown strike," he said. "There has been no confrontation with the officers . . . . Everything is cool."

The inmates are employed in the prison kitchen and mess hall and other facilities. Corrections officials said yesterday that the demonstration has caused only minor disruptions in the prison's operations and that inmates from other facilities may be brought in to do the work.

Officials said that the incident was the first significant work stoppage at the prison this year. Last November, about 300 inmates held a peaceful one-day work stoppage to protest a proposal to toughen D.C. parole guidelines. The guidelines had been developed at the insistence of Sen. Arlen Specter (R-Pa.), chairman of the Senate Appropriations subcommittee on the District, who said the D.C. Parole Board had been too lax in letting criminals out on the streets.

Yesterday's demonstration was staged in the six cell blocks that constitute the maximum security facility and that currently hold 536 prisoners. Some inmates have complained about the corrections department's increased use of shakedowns of prisoners leaving the dining area, in search of contraband knives and forks.

The inmates' list of demands includes a reduction in the frequency of shakedowns, the restoration of religious days for prisoners and their families, an end to the practice of shackling segregated prisoners when they have visitors and allowing inmates to receive one additional food package from home each month.