Former Alexandria prosecutor William L. Cowhig has been disbarred by the Virginia State Bar as a result of a 1975 incident in which the attorney received sexual favors from the wife of a defendant, individuals familiar with the case said yesterday.

The official disbarment order, which prevents Cowhig from practicing law in Virginia and may restrict his legal practice in other states, is expected to be made public in Richmond sometime next week.

Cowhig, 55, who resigned his office and left Northern Virginia last year after the woman's allegations became public, said he has not decided whether to appeal the decision. He declined further comment.

Cowhig, who practiced law in Alexandria for 25 years, was a member of the "good ol' boy network," a coalition of courthouse lawyers and politicans who controlled the city for decades. He went before the panel Nov. 20 to defend himself against the charges. Sources close to the investigation said the disciplinary panel agreed unanimously that the allegation of professional misconduct was serious enough to warrant the most severe punishment: disbarment.

The former commonwealth's attorney, who was acquitted of gambling and bribery charges growing out of an investigation of the city's bingo parlors, is unlikely to appeal the disbarment, a source said yesterday.

"I know he doesn't have any intention of coming back up here, or any intention of practicing law down there," the source said. "It's the end of everything."

The bar action marks the end of a two-year saga that saw Cowhig fall from his position as the Commonwealth's Attorney after fighting three felony charges stemming from the city's widely publicized bingo scandals.

Cowhig repeatedly denied any wrongdoing and was acquitted of bribery and illegal gambling. He resigned from office in February 1979 rather than face a third bingo-related charge and moved to Florida, where is now owns a bakery.

Cowhig's resignation came after a newspaper report that in 1975 he had solicited an act of oral sex from Sherry Rea Chenault, the wife of a drug defendant, in exchange for a promise of leniency. Chenault said the sex act took place in Cowhig's City Hall office.

The portly chief prosecutor denied the allegation, but reportedly told law enforcement officials during a 1975 investigation that some sexual activity had taken place. That information was suppressed by a member of the Alexandria police force.

Special prosecutor Claude M. Hilton was appointed to look into the sexual bribery charge and the police coverup. Hilton found no cause for criminal prosectution of Cowhig, but thought the matter serious enough to refer to the state bar. The Alexandria police official who admitted his role in the coverup resigned his post.

The bar action prevents Cowhig from practicing law in other states, such as Florida, which restrict lawyers who have been disbarred elsewhere, one attorney said yesterday.

A graduate of Georgetown University Law School, Cowhig was an assistant commonwealth's attorney for four years under Earl F. Wagner, then lost to Wagner in bitterly fought Democratic primaries in 1965 and 1969. In 1973 Cowhig, married and the father of three children, won the Democratic nomination and defeated Republican John E. Kennahan in the election.

In 1977, Cowhig ran unopposed for the $42,500-a-year post.