Mayor Marion Barry, at taxpayers' expense, has mailed 50,000 Washington residents over age 60 blue-and-gold embossed cards that are intended to give the recipients special discounts and services at restaurants and stores throughout the city.

But the effort to develop "The Mayor's Golden Washington Club" is encountering resistance from the merchants who are supposed to participate in the discount deal. About half the 1,500 businessmen contacted by the city so far have refused to take part, many saying the "club" is an overt ploy by the Barry administration to woo elderly voters. About 700 agreed to participate.

Richard Artis, director of the city's Office of Aging, which is handling the program, said his staff isn't keeping count of the reasons businesses offer for refusing to join the program, but he acknowledged that some merchants have simply said, "We don't want to do anything to help Marion Barry get reelected."

Older ciitzens are a significant force in city elections because they have a history of turning out to vote in large numbers.

Barry has devoted a considerable effort to winning support among older voters, and during his administration has substantially increased spending for programs for the elderly.

This week's mailout, 10,000 letters a day, was the latest step by the D.C. Office of Aging in a $250,000 campaign whose goal is to get more than 3,000 businesses to give discounts of varying kinds to about 100,000 senior citizens living in the city.

Businesses that agree to participate are asked to devise their own discounts for example, a restaurant might offer a two-for-the-price-of-one dinner during the early evening hours and will receive a window decal indicating that they are members of the program. Elderly residents would show their cards to obtain the discounted services or merchandise.

The merchants receive no pay from the city for participating, Artis said. The theory behind the program is that they will receive enough extra business to make the discounts worthwhile.

The city's $250,000 will go to print the cards, mail out letters, and pay the salaries of the staffers who are attempting to recruit businesss participants.

Artis said some merchants also have rejected the proposal because they believe older persons "don't need discounts because they have lots of money."

He said that argument has mostly come from shops or businesses in well-to-do sections of the city. Many of the city's elderly, Artis contends, are poor to middle-class persons living on fixed incomes.

The new members of the mayor's "club" learned of the program this week when they received letters welcoming them to the organization.

"Your enclosed Gold Card entitles you to special discounts and services among participating merchants across the city," the letter reads, closing with, "Please accept my thanks for your role in making this city a great place to live, Sincerely, Marion S. Barry Jr., mayor."

Artis said a number of businessmen "have asked if this is a political thing for the mayor." He said he tells those questioners the program has been in the works for 18 months and is not connected to the reelection effort. Some businessmen accept that explanation, he said, and some do not.

"Over time," Artis said of the doubters, "once they see this is for real they will rethink their positions." He said similar programs have been implemented in West Virginia and Ohio.

The West Virginia effort, known as the "Golden Mountaineer" program, was implemented by Gov. Jay Rockefeller during his 1980 reelection effort and was the subject of some debate in that campaign.

"Is this a one shot deal? No," Artis asked and answered. He said work on the program has been under way since 1980 and that funding for the effort is included in his agency's $14 million 1983 budget. "It'll be here no matter who is mayor," he said.

"I understand it the political wariness ," Artis said. "I wish I were fast enough to have it done earlier."

He said he "had some trepidations" about getting the program under way just as the mayoral campaign is heating up. However, he said he recommended to Barry that they go ahead, and Barry agreed.

"The program was in the works for a long time. It has come to fruition, and we are going forward," said Barry's press secretary, Annette Samuels. May was chosen to start the program because it is Older Americans Month, according to a city announcement of the program.