A broad-based, increasingly strident campaign against the proposed D.C. education tax credit is being orchestrated and financed by municipal labor groups that are telling their members that they will lose their jobs if the measure is approved by voters next Tuesday.

These unions and their allies among parent-teacher groups and civic organizations have unleashed a hail of campaign literature, radio ads and telephone calls to hammer home the contention that approval of the $1,200 tax credit would drain the D.C. treasury, cut city services and force 3,000 to 4,000 layoffs of city employes.

The main target of the antitax-credit campaign is the approximately 37,000 union members who are registered to vote in Washington. The largest group of them consists of D.C. schoolteachers and blue-collar city workers who belong to the local affiliates of the American Federation of Teachers (AFT) and the American Federation of State County and Municipal Employees (AFSCME).

"It's a very simple point we make: If our members vote 'yes' on the initiative, it means their jobs," said Geraldine P. Boykin, executive director of Council 20 of AFSCME, which represents about 10,000 city employes registered to vote. "It means layoffs not only in the schools but throughout the city, because it will erode the city's financial strength."

The unions' message drew a sharp response yesterday from a spokesman for proponents of the tax credit initiative.

"This is a scare tactic that government employes unions always use against any kind of proposal for a tax cut," said Kent Guida of the D.C. Committee for Improved Education. "It's their standard technique to try and create chaos and to throw the public into a panic. It's another way of avoiding talking about the issue."

Guida acknowledged that if the tax credit is enacted, some public school teachers might lose their jobs as some parents might transfer their children from public to private schools. "But as employment opportunities decline in the public schools, they will open up in the nonpublic schools," he said.

Opponents of the tax credit proposal are counting on support from middle- and upper-income white and black families in areas of Northwest Washington, where voter turnout traditionally is high (Wards 3, 4 and 5), and from black working-class families in Southeast Washington (Wards 7 and 8) who send their children to public schools.

Moreover, the opponents of the tax credit hope to win some converts among whites who live in near-downtown, "transitional neighborhoods" (Wards 1, 2 and to a lesser extent, Ward 6).

But Joslyn Williams, executive director of the D.C. Central Labor Council (AFL-CIO) and financial secretary of the D.C. Coalition Against Tuition Tax Credits, said that the basic strategy was to "bring out the areas of our basic support."

Rochelle Horowitz, political director of the AFT, the Washington Teachers Union's parent organization, added that the brunt of the opposition to the tax credit "has to be city workers, who would feel the crunch right away, and their unions."

The tax credit issue poses a major test of the political clout of Washington-area labor groups, which in recent years have had a dismal record of trying to affect the outcome of elections.

During the 1978 mayoral campaign, for example, labor backed Walter E. Washington in the Democratic primary, only to see Marion Barry win. The following year, labor lined up behind Douglas E. Moore in the race for an at-large seat on the D.C. City Council, only to see Moore get trounced by John L. Ray.

This battle against the tax credit has many of the trappings of a traditional political campaign without the candidates. There are large phone banks humming nightly, mass mailings of antitax-credit literature to union members and other potentially sympathetic voters, public forums, rallies and the planned deployment of sound trucks and door-to-door canvassers on election day.

Three separate organizations were formed this year to oppose the tax credit, including Save Our City (SOC), set up by city-elected officials and some labor leaders; the D.C. Coalition for Public Education, formed by the League of Women Voters and other civic groups; and, within the past two weeks, the D.C. Coalition Against Tuition Tax Credits, an umbrella group coordinating the overall attack.

Proponents of the tax-credit measure formally complained to the D.C. Board of Elections and Ethics on Monday that the antitax-credit coalition and the Washington Teachers Union failed to disclose how much they were spending.

They also asked the board to investigate a threat by Mayor Barry and D.C. school Superintendent Floretta D. McKenzie to mobilize the D.C. government in opposition to the credit.

So far, the most visible sign of campaigning in the public schools has been the distribution of antitax-credit leaflets to students by some teachers and members of the Parent-Teachers Association.

The leaflets carry such titles as, "The $1,200 Deception," "Initiative 7: You Have A Lot to Lose, Nothing to Gain," "Trick or Treat? The Truth About Initiative 7," and "Your Job Is On the Line In Tuesday's Election."

The three groups opposing the initiative said they would spend a total of about $75,000. But that figure does not include hidden costs, such as the full-time work against the initiative by paid staff members of the AFT and other unions and some mailing costs.

Two surveys conducted recently by the AFT and SOC revealed large pockets of opposition to the tax credit in Wards 3, 5, 6, 7 and 8 (Ward 4 was not surveyed). Opponents are expected to concentrate their get-out-the-vote efforts in those areas, using telephone banks and sound trucks to rally supporters.

An AFT survey conducted Oct. 18-20 identified 41 precincts where voters were likely to turn out in large numbers to oppose the tax credit, including the so-called "Bohemian" areas near downtown (Adams-Morgan, Mount Pleasant and Dupont Circle) and the heavily black, blue-collar sections of Wards 6, 7 and 8 in Northeast and Southeast Washington. In all those areas, opposition to the tax credit was running more than 2 to 1, according to an AFT official.

Wards 7 and 8 -- most of the city east of the Anacostia River -- contain the largest concentration of families who send children to the public schools. They also contain a large number of elderly persons who fear their property taxes will be increased if the tax credit is approved.

Opposition to the tax credit ran even higher in Ward 3, the area west of Rock Creek Park, and Ward 5, most of Northeast Washington west of the Anacostia River, according to a survey conducted by SOC last weekend, although many voters interviewed said they had not made up their minds yet.

Arrington Dixon, chairman of the D.C. City Council and a leader of SOC, said he was far less confident about the outcome of the vote, in part because of uncertainty over the impact of television commercials that proponents of the tax credit began airing on Monday.

Many in the antitax-credit camp hope to capitalize on what they claim is a voter backlash against the television commercials depicting the city's school system as ineffective and showing children allegedly smoking marijuana.

Robert Peterson, president of the Greater Washington Central Labor Council, said the ad is "tasteless, deceptive and contains racial overtones."

Peterson and Dixon sent separate letters yesterday asking local television stations to stop running the commercials, but managers of the three stations, WJLA (7), WTTG (5) and WRC (4), said they would continue the ads.

"It's an idea that people want expressed; it's a matter of public controversy and there are two viewpoints that deserve to be heard," said Jim Boaz, station manager of WJLA-TV.

Washington Post staff writers Lawrence Feinberg and Saundra Saperstein also contributed to this article.