Prince George's County Executive Parris Glendening has appointed a county police official to serve as interim director of security at the jail, after an escape there, an attempted escape and published reports of frequent sexual assaults among male inmates.

Glendening said yesterday at a press conference that he was departing from his policy of removing himself from daily government operations in order to address security problems at the county detention center.

The help of Maj. Michael Flaherty, 40, commander of the county's patrol officers, is "desperately needed," Glendening said. The deputy director's position that Flaherty assumes, second in command to jail warden Arnett Gaston, was created at Gaston's request shortly before the November elections, but has not been filled. Flaherty is expected to hold the position for several months until a jail security specialist is found.

In an apparent reference to stories in The Washington Post last fall in which inmates and guards said sexual assaults occur a dozen times a week, Glendening said yesterday that security at the detention center "is an extraordinarily undesirable situation that has been well publicized." He said that both Gaston and police department officials had recommended that the security position be filled immediately.

Gaston said yesterday that he was "very happy with the appointment ." He continued, "I have known Mike Flaherty for a long time and feel he is a dynamic person whose management philosophy is consistent with mine."

Gaston added that Capt. Edward Blakeslee, who has been running the jail's security division in an acting capacity for the last 18 months, will return to his old position as physical plant director.

The county's jail, located in Upper Marlboro, has suffered from several problems in the last year, primarily an escape of nine inmates on July 8 and an attempted escape by five inmates Aug. 20, as well as the sexual assaults.

When reporters questioned Glendening at the press conference about whether Flaherty's appointment indicated Gaston might be replaced, the executive said that he has not made a decision on that issue.

Glendening, newly elected in November, has said privately that he wants to give Gaston time to prove himself. Glendening has also said he wants to determine whether problems in the jail's administration stemmed from a lack of support from the previous county executive. Gaston has taken several steps to reduce the number of sexual assaults since The Post's series ran.

However, Glendening has also said that he was displeased with Gaston's public denials of security problems after The Post's stories on inmate rapes.