This old, puritan city's bold experiment to deal with commercialized sex by legitimizing porno stores, strip clubs and X-rated movies in one downtown area has simply not worked.

The officially sanctioned "adult entertainment district," better known locally as the "Combat Zone" and often promoted as a solution other cities could emulate, still exists. But the policy of activity upgrading the area, to make it safe and attactive and to keep "adult" businesses from spreading, has been all but abandoned.

Last week, it has been learned; an in-house task force report outlining alternative uses for the Combat Zone area and suggestions for encouraging physical improvements in surrounding areas, was quietly delivered by staff aides in the Boston Redevelopemnt Authority, the city's planning agency, to authority director Robert Walsh.

The report apparently makes no specific recommendations about changing the city's policy toward adult uses. It does, however, offer the real possibility that the Combat Zone is dying on its own, under the presures of the private marketplace and stepped-up law enforcement.

Walsh "has said many times that the whole area potentially has been a site for other kinds of development years in the future," authority spokesman Ralph Memolo said. "The change is the perception that that time may not be so far off."

Three years ago, the zoning board, encouraged by then BRA Director Robert Kenney, designated the seedy lower Washington Street area ordering Chinatown and the downtown shopping district, and a block from the theater district and Boston Common, as the only zone in the city where adult uses would be allowed. The zoning was combined with a new federally funded city park - "Liberty Tree Park" - and a push to get zone businessmen to clean up the area and construct new, attractive facades for their operations. Kenney even tried to change the name of the Combat Zone to "Liberty Tree."

"Within a year or so the term Combat Zone will be a thing of the past in Boston," he predicted at that time.

But these plans went awry, as much the result of lax law enforcement creating an "anything goes" atmosphere that attracted aggressive prostitutes and muggers to the Combat Zone as of continued refusal by Zone entrepreneurs to change their business habits.

"The zoning has succeeded as far as containing adult activities in the area, where they already existed," said Walsh. "Where it's been a failure has been in enforcement. There was an obvious tendency for illegal uses to go down there, which unfortunately, after same traumatic events, resulted in more aggressive enforcement of laws already on the books."

Those traumatic events included the release last December, by resigning police commissioner Robert diGrazia (now police chief of Montgomery County, Maryland), of an internal investigative report citing acts of "obvious gross incompetence" and "corrupt inattention" to duty by the patrolmen and command staff of Police District One, which covers the Combat Zone. Then, two days later, Harvard football star Andrew Puopolo was fatally stabbed in the Combat Zone.

These events resulted in a crackdown that today finds most Zone liquor establishments with their licenses either suspended or revoked, the result of dozens of violations ranging from inadequate lighting to prostitution on the premises. The remodeled Two O'Clock Lounge, so-called "flagship" of the Zone, has its license suspended for 30 days by the state and may not reopen because it also faces a license revocation from the city's licensing board. Last week, the licenses of two other bars were revoked for allegedly being centers of prostitution.

Some reports are that combat Zone proprietors have begun leaving the city, moving their operations to a string of rowhouses along ROute 1 in Peabody, a North Shore suburb. There, they face a newly adopted ordinance forbidding nude dancing in lounges.

Even though Walsh stresses that the official policy remains unchanged, the city has already altered course by encouraging private development on all sides of the zone which will hem it in and shrink it in size and possibly wipe it out.

On one side, the Combat Zone is to be abutted by lafayette Place, a $175 million shopping and hotel complex extend the renovated downtown shopping district. In nearby Park Square, a $150 million renewal project, Park Plaza, awaits official approval. The expansion of Tufts New England Medical Center is moving in on the zone from another side.

Additionally, whole blocks within the Combat Zone, now devoted almost exclusively to adult uses, are being bought up by the neighboring Chinese community group, meanwhile, is negotiating to purchase another block in the heart of the Combat Zone.

Reacting to these developments, Boston Real Property Commissioner Joanne Prevost tipped her hand recently on where she thought the Combat Zone was headed. Appearing before the Air Pollution Commission to seek approval for a new parking garage in the Lafayette Place complex, she said, "With this moving down the street, and Tufts moving up the street, that whole detrimental aspect of the Combat Zone will soon not be there."

Still, Walsh insisted there has been no policy change.

"My posture at this point is not to change the zoning and see what happens with the private marketplace," he said. As the zone dies of its own, however, fears are surfacing that the North Station area, with a pair of adult moviehouses already, will become the new Combat Zone, a phonomenon for which the city has no strategy.

"Trying to abolish these uses through redevelopment is like trying to grow a garden without weeds," offered one BRA source. "You can always try, but just turn your back for one minute, and there they are again."