Dale E. Friesz, one of Fairfax County's top administrators for the last 10 years, has resigned over what some described as a "semibelligerent" and "abrupt" speech he made to a citizens group last February.

Friesz, 38, whose resignation as director of county personnel becomes effective June 29, quit after a March 5 meeting with the county's Board of Supervisors at which board members reportedly voiced dissatisfaction with his conduct.

The action followed Friesz's appearance Feb. 28 before the Committee of 100, a nonpolitical organization of citizens interested in county issues, at a Merrifield restaurant.

A member of the group, who requested anonymity, said yesterday that the speech, which dealt with a Justice Department discrimination lawsuit pending against the county, was delivered in a "semibelligerent" and "abrupt" tone.

"I remember thinking that man doesn't like his job," the person said.

According to another source, who also asked not to be identified, Supervisor James Scott (D-Providence) was present during Friesz's presentation and later brought the matter to the board's attention. Scott yesterday would neither confirm nor deny that he attended the meeting.

Friesz yesterday also declined comment, except to say that he resigned the $44,000-a-year post because "all things good and bad must come to an end. It's time for another job." He refused to elaborate on his plans.

Friesz added that he thought he had been "a damn good personnel director" and was proud of his accomplishments. "We've got the best personnel system in the state," he said.

Friesz subsequently sent a letter of apology to the group, according to one member, who said the organization was told Friesz "had been under a tremendous amount of stress and strain."

The boyish-looking Friesz, who started work in the county personnel office as a trainee at age 22 and became director six years later, was responsible for overseeing 6,000 staff employes.

The county's employment practices came under attack in December in a Justice Department discrimination suit and Friesz had spent "a length of time" providing data for depositions in the case, county spokesman Edmund Castillo said yesterday.

Others familiar with the county government said Friesz was unhappy at the growing role of the Fairfax Civil Service Commission and the supervisors in personnel matters.

Before a Virginia Supreme Court decision in January 1977 outlawing collective bargaining for county employes, Friesz had represented the county in labor negotiations.

Theresa Gregory, a member of the five-member Civil Service Commission, denied yesterday that there was any friction between the commission and Friesz. "The commission has enjoyed a good rapport with Dale Friesz," said Gregory, who said she was sorry to see him leave.

Castillo said Cornelius J. O'Kane, Friesz's assistant, has been named acting personnel director until a successor is selected.