The Montgomery County chapter of the Fraternal Order of Police announced yesterday that a majority of its members had voted "no confidence" in Chief Robert diGrazia, citing "frustration and dissatisfaction" with his leadership.

There has been a simmering discontent in the 750-man department over diGrazia's policies for several months, but the vote by about 300 members of the FOP Monday night marked the first public denouncement of the chief by the police officers under his command.

DiGrazia responded by calling many of the group's charges invalid and saying he would be "more concerned about a no confidence vote of the citizens" of the country.

The vote marked the second time in the past six weeks that members of a police force in the Maryland suburbs have voted on confidence in their chief.

In Prince George's County, the Fraternal Order of Police last June 29 blamed Chief John W. Rhoads for not giving them moral support in their fight for a new contract and for firing a police officer who had shot an unarmed shoplifting suspect.

Lenny Simpson, president of the Montgomery FOP, cited nine items that he said were at "the heart of the police officers frustrations," but long-time lack of promotions and a recent report critical of the officers' four-day work week were the central focus of his remarks.

Simpson said the last promotional exam in the department was given in September 1975 and that there have been no promotions in the lower ranks since then.

"The continued indifference to the lower ranking officers can no longer go unchallenged by our organization," Simpson said during a hastily called news conference on the steps of the Rockville Mall.

Simpson said the officers are "very concerned" about keeping their present four-day 10 hour-a-day work week. He charged that a recent police department report critical of the four-day week was based on "outdated and inadequate data."

"These officers want to keep the four-day work week," Simpson said. "Many depend on it in order to keep a second off-duty job."

In a press conference immediately following Simpson's, an unruffled diGrazia responded by saying that "around budget time or in election years, you'll always hear comments that 'morale has never been lower.' Look over the last 15 years and you'll find them."

As to the FOP's anxiety about the four-day work week, deGarzia asserted: "Let me state that they should be concerned. The fact is, that the present plan suits officers' needs more than the community's needs."

A recent department study, diGrazia said showed that "there were inadequate numbers officers on duty during peak crime periods.

"If there are not officers on the streets during peak hours then citizens' and officers' safety is in jeopardy," he said.

He added that he is considering alternative shift plans, but would take no action until he gets input from police officers themselves.

Simpson, however, has charged that the police department study was based on "outdated 1977 data" and did not take into consideration whether the calls for service concerned serious or routine matters.

On the question of promotions, diGrazia said he is "concerned about career advancement and promotions for police officers" and wants them "to follow a plan and be consistent with the goals of this department."

DiGarzia, since his appointment as chief in November 1976, has made fewer than a dozen promotions because of his concern about the validity of previous promotional exams and charges of cheating on some of the exams, according to aides.

Yesterday, he said he does not want to take a "Band-aid approach" to promotions before the county Personnel Board acts on a new department plan for sweeping changes in police job descriptions and promotions. The plan, which he said was devised with input from the Simpson's police group, has been in the board's hands since last March.

"Why take it out on me because the Personnel Board hasn't acted?" diGrazia asked.

DiGrazia also said he felt the many of the charges were politically motivated - Simpson's response to FOP member's pressure for action.