Alexandria's former prosecutor William L. Cowhig was absolved yesterday by a special prosecutor of charges that he solicited and accepted a sexual bribe from the wife of a drug suspect.

Special prosecutor Claude M. Hilton said that "certain acts" - described previously as an act of oral sodomy - which occurred between Cowhig and the woman did not "add up to" a crininal offense. Hilton said the incident should be investigated by a disciplinary committee of the Virginia State Bar.

In a report filed in Alexandria Circuit Court, Hilton concluded a three-month long investigation of the 1975 incident, saying that Cowhig's behavior "raised questions as to the ethics or the propriety of such conduct of a lawyer who is commonwealth's attorney."

He said he had forwarded "certain information" about the incident to the bar, which already has begun an investigation that could lead to disbarment proceedings against Cowhig.

Cowhig 53, resigned as the city's prosecutor Feb. 23, six months after he was indicted by a state grand jury on three felony charges growing out of the operation of large-scale bingo games in the Northern Virginia City.

He was acquitted on two of the charges after emotional trials and resigned rather than face trial on the third charge.

Cowhig vehemently denied both those charges and the sexual bribery allegations, accusing his critics of attempting to drive him from the $42,500-a-year prosecutor's job.

His potential legal troubles were not ended by Hilton's report. A U.S. grand jury in Alexandria, probing allegations of corruption among city officials, is known to be looking at Cowhig's activities.

"I just want to thank Mr. Hilton for a thorough and fair investigation," Cowhig said yesterday. He added that he considered himself "retired" and spends most of his time "playing golf at the Belle Haven Country Club," south of Alexandria.

Others were less satisfied with Hilton's report. It was branded "a plain, ordinary cover-up" by Alexandria City Councilman Donal C. Casey, who has been outspoken in his criticism of Hilton's handling of the case.

"He [Cowhig] disgraced his office, disgraced his profession and now he will receive no penalty," Casey said in an interview. "Hilton . . . didn't look at anything."

Alexandria police were also cleared by Hilton of any criminal conduct in connection with the case. In 1975, Cowhig voluntarily submitted to a lie detector test to prove his innocence of the sexual bribery charge. Although Cowhig reported that he had "passed" the test, sources have said he admitted to the polygraph examiner in a pre-test interview that sexual activity with the woman had occurred. Cowhig told the examiner that the act of oral sodomy had not been completed, according to the sources. Cowhig also stressed that no promise of leniency had been made in exchange for the sexual favor, the sources said.

Details of that interview were ordered suppressed in 1975 by Capt. Norman E. Grimm, who resigned from the force in March, admitting his role in what was called a "cover-up."

Hilton said yesterday he was "satisfied" with the internal police investigation that led to Grimm's resignation.

Alexandria lawyer Philip J. Hirshkop, chairman of a bar committee considering the Cowhig case, declined to comment yesterday, saying all discplinary matters are confidential. However, sources said a hearing into the matter was imminent.

The 1975 allegations against Cowhig, made by Sherry Rae Chenault, resurfaced last summer during a police investigation into Cowhig's role in the city's bingo scandal. At that time, the polygraph examiner disclosed the contents of the pretest interview, which had remaiend suppressed for three years.

In February, Cowhig's former deputy, John E. Kloch, who had assumed the chief prosecutor's job pending the outcome of the Cowhig trials, asked Alexandria Chief Circuit Court Judge Wiley R. Wright to appoint a special prosecutor to investigate the alleged "prosecutorial misconduct" and police cover-up.

Hilton, 38, who served as Arlington's chief prosecutor in 1973 and 1974, was appointed. His duties were concluded with yesterday's report.

Saying he felt no animosity toward anyone, Cowhig said he plays golf twice a week, reads the bible and attends mass daily to "thank God for his goodness."

Chenault's husband, who pleaded quilty to drug charges in 1975 and was not offered any leniency, has filed papers in Alexandria Circuit Court seeking his release from prison. Dnaiel Wayne Chenault's writ of Habeus corpus was filed on the grounds that he and his attorney, Roger L. Amole, were given false information at the time of his trial by the prosecutor's office headed by Cowhig.

Chenault currently is serving the end of a five-year prison sentence at a Fairfax work camp. He charged in court papers that the Alexandria police and the Commonwealth's Attorney's office "conspired to cover up" details of his wife's allegations against Cowhig. CAPTION: Picture, WILLIAM L. COWHIG . . . absolved of sexual misconduct