A former District of Columbia massage parlor owner, who openly vowed he would never pay the city the $150,000 in back taxes it says he owes, yesterday was fined $15,000 for his boastful violation, but still does not have to pay the taxes.

The city, which has never sent anyone to jail for failure to pay D.C. taxes, has sought to give Harold Johnson O'Brien, described by prosecutors as the city's biggest tax scafflaw, the dubious distinction of being the first.

But after an hour-long D.C. Superior Court hearing, in which O'Brien's attorney asked leinency for her client because she said he has cancer, Judge John D. Fauntleroy handed O'Brien a suspended 11-year jail term and a $55,000 fine, suspending all but $15,000 of it, and placed him on three year's probation.

"Harold O'Brien has led a charmed life," Assistant D.C. Corporation Counsel Lawrence B. McClafferty said before the hearing. After the sentencing, the same prosecutor refused to comment on the judge's sentence as he left the courtroom.

Officials said that it would be fruitless to attempt to collect the money O'Brien owes by attaching his property because he apparently now has almost nothing in his name.

O'Brien, 49, is a tough-talking, round-faced businessman who once ran as many as six business enterprises producing hundreds of thousands of dollars in revenue, prosecutors said.

O'Brien said that at one time or other he operated a successful sexually oriented massage and escort service, a computer dating service (he was the computer) and a photo-copying company with such clients as Ralph Nadar and large downtown law firms.

He became controversial because he oepenly flouted the city's tax system, refusing to file or pay his District taxes or business taxes for his copying firm. He was convicted on those charges last month.

O'Brien claims the city has a vendetta against him. "Because I waved the flag, the city said 'We got to teach this guy a lesson."' He called his prosecution "political."

Barbara Kammernnan, O'Brien's attourney, told Fauntleroy that O'Brien should be able to go Massechusetts and live with his sister, a suggestion McClafferty acknowledged, in court papers, that the city singled out O'Brien for prosecution after O'Brien publicized his refusal to pay taxes. "The defense suggests," McClafferty told Fauntleroy, "that the appropriate punishment for successfully evading taxes in the District of Columbia for over five years is to be sent to live with your sister in Massachusetts."

O'Brien sat quietly in the courtroom yesterday as his attorney described his exploits in 1972 when he helped police capture a bank robber and recieved a letter of commendation from then-chief of police Jerry V. Wilson for his efforts.

"I'm a non-conformist," O'Brien said in an interview. "I don't go around hitting people on the head. I'm not dangerous. I'm not a murderer. I'm not a bank robber -- in fact I captured a bank robber." He seemed relieved when he learned that he would not have to go to jail.

O'Brien claimed at his trial that he should not have to pay his District taxes because he lives at an undisclosed location in Virginia or Maryland, a contention disputed by the government, which said he is a D.C. resident.

Prosecutors said they first learned O'Brien was "bragging that he didn't pay his taxes, that he never had and never will." A tax revnue agent was sent to O'Brien's office. But O'Brien proudly says he threw him out.

During the trial, city tax officials testified that their records showed that O'Brien had never paid city personal income taxes since he became a D.C. resident in 1963. They also said O'Brien refused to pay income taxes on his business from 1973 to 1975.

Evidence submitted at the trial showed that O'Brien sometimes earned more than $90,000 a year in personal income during that time. Prosecutors said recently they estimate O'Brien owes the city at least $150,000 in taxes. s

The O'Brien case, prosecutors say, was one of about two dozen in the last year. According to D.C. tax officials, about 200 city tax cases have been prosecuted since 1976 and the city has collected $70,000 in fines. The average fine in the case, which include both individuals and companies, was $537.

The fact that the city has never sent anyone to jail for willful failure to pay taxes is a "dismal point," said Stan Jackson, an official with the city's Department of Finance and Revenue. "The statistics are embarrassing."

As part of its attempt to increase the number of tax prosecutions, Jackson said a larger unit has been established to investigate cases before they are submitted to the D.C. corporation counsel's office for prosecution.

One of the problems according to tax officials, is the city's lack of resources to investigate and discover cases.

"Harold O'Brien was right," said one official, "if he had not opened his mouth, he'd still be making a handsome income."