The largest union in the AFL-CIO has sounded its latest battle cry though the angry voice of a little grey-haired lady wearing a floral print dress and pearls.

Occasionally brandishing a frying pan or waving the American flag, the television character Mama stars in a new series of TV and radio commercials for the United Food and Commercial Workers International Union.

With her blend of cantankerous humor, Vicki Lawrence -- the Mama of the NBC network comedy -- is pitching the union's message on trade and labor issues to a new generation of workers and to sections of the country where union strength is weak. Mama buys American products. She refuses to cross picket lines. She scolds people putting up with low pay and poor working conditions and tells them to join a union. Old messages, but delivered in a more effective way to new targets, the UFCW strategists hope.

The Mama campaign also illustrates a sharp change in the AFL-CIO's strategy for revitalizing the declining strength of the union movement nationwide. The strategy, pioneered by the UFCW, is based on a direct appeal to the public for support and a more confrontational battle for new members in the growing industries of the service economy, using traditional economic pressure tactics such as consumer boycotts and informational picketing. Both approaches are intended to counteract labor's declining status with the public and a string of setbacks in the courts and federal agencies.

The UFCW, with 1.3 million members, has grown to be the largest union affiliated with the AFL-CIO by organizing large groups within the service sector. Representing grocery store workers, retail clerks, insurance, financial and health care employes, the union has increased its membership 31 percent in the last two years, while the AFL-CIO's total membership has remained virtually unchanged at 13.8 million members. The UFCW's success has made it a model for the rest of the AFL-CIO, one union leader says.

Mama represents "an entirely new communications approach" for the union in two ways, UFCW President William H. Wynn said when the commercials were first introduced last month.

First, the union spokeswoman is a television character in a popular weekly series. Created by Lawrence years ago in comedy skits on the Carol Burnett Show, Mama is familiar and appealing. Like cranky old matriarchs in any family, she can speak her mind in an authoritative, no-nonsense way, according to union strategists.

Second, Mama is funny. She represents a serious decision by the union to reach people through humor.

"Listen, lamebrains," Mama says, in one commercial aimed at discouraging business at foreign-owned supermarket chains. "Here's the problem: Imports. We've got foreign cars, foreign TVs. Foreign radios. What we don't need is a bunch of rich foreigners sashaying over here and telling us how to run the whole dang supermarket. I say stick it in your frozen foods. This is our flag. And it means life, liberty and the pursuit of happiness. You can't pursue diddly without a job."

Through humor, the union hopes to engage viewers who otherwise might resist a serious union message.

"Today's labor issues are no laughing matter," Wynn said. "But with a judicious use of humor, we hope to communicate serious issues in a way that the public will pay attention, understand and remember our message, and react."

Wynn also noted the success of Wendy's "Where's the Beef" commercials and the obvious parallels to Mama. "Far more people heard the slogan than saw the ad. By creating catchy and humorous spots, we hope to take advantage of the same phenomenon. After seeing our ads, we hope people will remind each other what Mama told them," he said.

"Labor's message traditionally has been moralistic and preachy," said Allen Y. Zack, communications director of the UFCW. "We wanted a character who could come out and say 'that ain't right.' "

The union also wanted a character that would work on television. Many TV stations refuse to run labor commercials because they fear the spots will cause controversy or alienate viewers and irritate advertisers, Zack said.

"Everybody's got an aunt or mother or grandmother who acts like that," Zack said. "Even yuppies have mamas."

To bridge the generation gap, the commercials show an angry Mama, followed by a smiling Vicki Lawrence as herself. Lawrence says "listen to Mama. Be American. Shop American," or "listen to Mama. A union can help. I know. I belong to four. The UFCW is one of the best. Call and find out."

The Mama commercials started running July 18 in Augusta, Ga., as part of the UFCW's campaign there against the labor practices of foreign-owned supermarket chains. Two of three stations in the area agreed to run the commercials, the union said.

In Augusta and nearby Atlanta, the UFCW is campaigning against nonunion supermarkets owned by a company based in Belgium. The union fears that the nonunion stores will take business away from supermarkets that employ UFCW members, and that those workers will lose jobs.

The communications campaign includes a heavy dose of pro-American, antiforeign symbols and rhetoric. The commercials include tag lines urging listeners "to please don't shop at the foreign-owned Cub store," or to "shop at Kroger -- it's American."

One red, white and blue handbill distributed outside a nonunion supermarket bears an American flag and words "Say, 'NO!' to foreign companies that want to throw American workers out of Jobs! Please do not patronize this foreign-owned store."

The theme is used as a weapon against specific grocery chains and as a way to reach potential members and supporters. The commercials seek to reinforce, or instill, the idea that unions are part of the American tradition. "Respecting picket lines is as American as apple pie," Lawrence says in one commercial.

Unions have used television and "Buy America" campaigns before, to combat job losses in the auto and steel industries. But with more industries and regions hurt by the country's worsening trade imbalance, such themes carry more power. "People are very receptive to the issue," said Frank R. Dininger, director of the UFCW's southeastern region, noting that textile workers and shoe workers in the region are particularly angry about imports.

The economic reasons for rising imports and foreign investment are complex. And the union acknowledges that most of its complaints against the Belgian-based company have more to do with its labor practices than with its nationality. The campaign does not tell people to boycott foreign-owned -- but unionized -- grocery stores. But the issue is an available weapon. "We would have been out of our heads not to use the foreign issue," Dininger said.

The United Auto Workers union has launched a nationwide television campaign tracing the union's 50-year history and centered around the theme of "proudly building America's future." Last week the UAW began showing a series of commercials filled with flags, families and song.

One goal of the UAW ads is to make people "feel better about unions" by showing "the very positive role unions have played in America beyond the workplace, in the members' lives and in the community," said Frank Greer, president of Greer & Associates, which developed the campaign.

The UAW campaign also includes shots of the space shuttle and states the union's involvement in "training for new technology," an effort to combat the idea that unions resist change, Greer said. The UAW, which represents aerospace workers, "feels very strongly that unions are not holding back productivity," Greer said. "We want to be competitive."

While the AFL-CIO has urged all its constituent unions to improve their communications, the organization also has directed its affiliates to back up the glossy image with tough tactics. Noting the frustration of many unions with the National Labor Relations Board, the AFL-CIO has encouraged unions to return to traditional forms of economic pressure to battle management. Such tactics include boycotts, picketing and other methods of turning public opinion against a company to cut into its earnings.

"The NLRB has no teeth, so we have to grow our own teeth," Dininger said.

The Mama commercials are designed to supplement such tactics, Zack said. In Atlanta, Mama is supported by pickets, handbills, mailings, and radio and newspaper ads detailing the union's complaints and encouraging consumers to boycott certain stores.

Local units of the UFCW must organize such "total" campaigns if they want to use the Mama commercials, Zack said, describing the Mama commercials as a "carrot" being offered to the locals.

"I don't believe 'image advertising,' per se, will be helpful to labor. If labor is to be successful, it must be an aggressive, effective organization for its members," Zack said.

UFCW officials credit economic pressure tactics with reversing a decline in the union's membership growth in the early 1980s. After reaching a low of 38,940 new members nationwide in 1980, the union grew by 58,841 members in 1983 and by 65,245 members last year.

The union's southeastern region, comprising Georgia, North and South Carolina, Florida, Tennesee and Alabama, had 60,000 members last year and expects to add 12,000 members this year.

The UFCW's success is striking at a time when the AFL-CIO's total membership remains unchanged and unions as a whole represent a shrinking fraction of the work force. Gains by service unions have just about offset the loss of jobs in the industrial Northeast, but have not kept pace with the total growth of jobs in the economy.

The total number of unionized employes has remained steady since the mid-1950s at between 15 million and 17 million. However, union members have declined from 28 percent of the private-sector work force in the mid-1950s to about 18 percent in 1980 and about 16 percent currently, according to Marvin Kosters, an economist with the American Enterprise Institute.

Manufacturing or goods-producing industries employed 25.3 million workers last month, up 15 percent since July 1965. The service-producing industries employed 73 million workers last month, 87 percent more than in July 1965, according to the Bureau of Labor Statistics.

Organizing the service sector is not easy, Kosters said. Much job growth has been in the South and Southwest, which always were less unionized than the northern industrial cities, he said. Many new industries lack union traditions. Even service industries with strong union histories, like transportation and utilities, have seen membership drop with deregulation, he said.

Although the service sector includes some highly organized groups such as teachers and other government employes, it is "probably not fertile ground for unionization," Kosters said.

The UFCW disagrees. Although it is too early to judge the results of the Mama campaign in Augusta, the local UFCW union claims it has 90 percent membership in the stores it has organized in the Atlanta area.

Dininger and Jerry M. Hardin, president of Local 1063 near Augusta, say the union gets more calls from the South than anywhere else because the union has been both effective and visible there.

"The fact is, we're going to get more aggressive than we have been," Hardin said. "Our good days are ahead of us."