Courting the approval of a skeptical Senate subcommittee, city officials yesterday disclosed revised plans for a proposed Washington Civic Center that would be somewhat smaller, somewhat cheaper and as controversial a ever among its detractors.

But the officials, who held a special briefings in the City Council chambers yesterday, did not offer specific information about what, if any, privately financed projects - termed "spin-off" development - will result from center's construction.

Without commitments for such revenue-producing projects from the business sector, Sen. Patrick Leahy (D-Vt.), chairman of the Senate D.C. Appropriations Subcommittee, has said he will not approve funds for the center for fear it might become a financial drain on the city.

City officials, attempting to alleviate some of Leahy's concerns, said yesterday they have cut total cost of the project from nearly $116 million to about $98.7 million and reduced its size by about 50,000 square feet.

They promised that specific development projects would be announced by the time the city sends its revised center plan to Leahy's subcommittee in mid-September.

The two-level concrete structure would be located in a three-block area south of Mount Vernon Square bounded by New York Avenue and H, 9th and 11th Streets NW. The center is intended to attract up to an estimated 390,000 new convention visitors to the city each year and to increase city tax revenues by an anticipated $12 million annually.

Projections for the center's convention attendance and financial success have been challenged by a number of community groups and political candidates, and many of them showed up at the briefing yesterday to quiz officials about the new proposal.

In short but heated exchange with a member of the audience, City Administrator Julian Dugas angrily told one civic activist, "I'll cut you off," as the man persisted in asking questions about the project.

In a calmer atmosphere earlier in the briefing, Municipal Planning Office Director Ben Gilbert said the convention center project "remains viable" despite the reductions in cost and exhibit space.

"Clearly, the task became one of building an acceptable, more tightly designed center with a reduced program to make possible desired economies," said Gilbert. He said a special city government task force had worked all summer to meet Leahy's conditions for approving the center.

An aide to Leahy declined yesterday to discuss the city's latest convention center plan, saying the senator would be holding hearings on the complete proposal once he receives it.

On Thursday, the city will hold its own public hearing on the project to allow citizen groups to voice their opinions. The hearing will be in two sessions, beginning at 2 p.m. and 6 p.m., at the Martin Luther King Jr. Library.

With its main visitor entrance on Ninth Street, NW, the proposed civic center would have total exhibit space of about 259,000 square feet, including two exhibition halls.

One the civic hall, would seat 10,000 to 12,000 persons for a national convention or civic event, Gilbert said. He added that "no such hall that size currently exists" in the District of Columbia.

The hall is designed to be used for conventions and civic meetings when not in use for trade shows of exhibitions.

Another section of the center, reffered to by Gilbert as the main exhibition hall, would have 151,000 square feet of space by removing sliding walls separating the main hall from the smaller civic hall.

In addition to the exhibition rooms, the center would contain an additional 28,000 square feet for a meeting room with modern audio-visual equipment.

Comer Coppie, director of the D.C. Office of Budget and Management Systems, addressed the center's financing program.

Noting the proposed project is a year behind the original date for construction to start, Coppie said the same center that would have cost nearly $109 million a year ago would cost nearly $116 million today.

Thus Coppie said, the city had actually reduced the center's cost by more than $17 million with its revised proposal. In addition, he stressed, the new figures have reduced the long-term borrowing requirements from $106.9 million to $77.3 million.

The $77.3 million figure is what remains to be borrowed to build the center once $21.4 has been spent to acquire the construction site.

The building site would be purchased with funds raised by a recently enacted hotel room occupancy tax and a 10 percent surtax on corporation and unincorparation business incomes. One-half of these revenues is earmarked for the center.

Coppie said the city would experience a $8.7 million loss in financing the center in 1979, an amount he said would gradually be reduced until mid-1982, when the city is fully operatiional. By then the city would show a net gain of $3. 9 million.

The deficits could be reduced, Coppie said, by changing the tax law to divert more money from the hotel tax and surtax to the center project.

Yesterday's briefing broke into a shouting exchange for a short time when city administrator Dugas, chairman of the civic center task force, clashed with some of the project's opponents.

Marie Drissel, a member of the Convention Center Referendum Committee, which is seeking to place the issue on the ballot, complained that it was difficult to judge the likely employment picture for D.C. residents without knowing what new development might result from the center's construction.

City officials estimated about $7.5 million in spin-off development will be needed to satisfy Leahy's concerns, but Dugas said information on the projects "is just not going to be revealed today."

When Dugas recognized at-large City Council candidate Betty Ann Kane for another question, Kane demurred, saying she did not want to cut the other questioner off.

"I want to cut her off," Dugas said.

Moments later, Bert Anderson, another member of the referendum committee, complained he couldn't get another question answered because "you're cutting us off." Dugas replied angrily, "I'll cut you off."

"That is hostile," shouted Carol Gidley, an Advisory Neighborhood Commission member from Friendship Heights and American University Park.

Gidley and others complained afterwards of Dugas' "hostile and arrogant" manner. Gilbert said yesterday's briefing was not intended to be a hearing.

The civic center proposal has support of Mayor Walter Washington, the majority of the city Council and the city's business community.

Leahy, however, has long expressed reservations about the project and last year killed start-up funds for its construction in the D.C. budget.

The Vermont senator eventually agreed to resurrect the proposal a few months ago if city officials would reexamine its design and cost estimates and secure private business investments in related developments to offset initial financial losses the center is expected to encounter.