Five remaining misdemeanor charges brought against Alexandria massage parlor attendants as a result of an undercover investigation that used a civilian volunteer, were dropped yesterday by city prosecutors.

According to City Manager Douglas Harman, the last of the original 13 cases were dropped after a closed-door meeting between City Atrorney Cyril D. Calley, Police Chief Charles T. Strobel and Harman. The manager said the officials have been "frustrated" by police attempts to crack down on Alexandria's once-flourishing massage parlor trade.

"That pretty much ends it from a criminal standpoint," said Assistant City Attorney Nolan Dawkins after Circuit Court Judge Donal Kent accepted the city's motion to end the cases.

Frederick Ford, the attorney representing the five masseuses, had filed a motion arguing that the use of the circuit Court Judge Franklin P. Backus as bsis for his motion. In August, a case against one of the masseuses was dismissed when the Fairfax judge, sitting in Alexandria said he could not decide "who was the bigger whore," the masseuse or the undercover volunteer. Two years ago, Judge Backus also ruled that use of a civilian volunteer who undresses and participates in an illegal sexual act constituted governmental misconduct.

Of the 13 case brought about as a result of this year's undercover investigation, only two have gone to trial, resulting in one conviction.

Ford said yesterday he is still considering filing criminal conspiracy charges against those officials who sanctioned the use of the volunteer. When asked if the decision to drop the remaining cases was based on Ford's previously announced threat, Harman said, "No. The decision was based on the judge's ruling of this summer."

The city manager said a new massage parlor ordinance also was discussed at yesterday's meeting. That measure, approved by the City Council last week, places restrictions on an establishment's hours of operation as well as empowering the city's health director to revoke a health permit if massages between members of the opposite sex are found to occur in the parlors.

Immediately after the passage of the new law. Ford labeled the legislation "unconstitutional" and "unenforceable."

City officials said yesterday they have not yet decided on methods to enforce the ordinance and said no action has yet been taken against any of the city's massage parlors or so called "health clubs" under the new law.

Separately, the man who directed promotional activities for what the FBI said was the "largest and most sophisticated commercialized prostitution business" in the Washington area yesterday pleaded guilty in U.S. District Court in Alexandria to the charge of interstate travel in aid of racketeering.

Baron M. Lyhne, 33, was the fifth person formerly employed by Michael Louis Parrish, to plead guilty to interstate racketeering charges in connection with an investigation of businesses run by Parrish.

Lyhne agreed in court yesterday to statements made by Assistant U.S. Attorney Henrey E. Hudson that he directed promotions for Parrish and sent people from Northern Virginia to the District of Columbia to distribute cards and leaflets advertising massage parlor services.

Those serivces, Hudson said, involved prostitution.

U.S. District Judge Albert V. Bryan Jr. set Lyhne's sentencing for Jan. 19. Lyhne faces a maximum penalty of five years in prison and a $10,000 fine.