Labor leaders yesterday criticized Mayor Marion Barry for allowing the Adolph Coors Co., subject of a boycott by organized labor, to pay for a reception Barry gave Saturday night for several hundred supporters and friends attending the Congressional Black Caucus weekend.

Coors, which is a client of the public relations firm of which Barry's wife Effi is a vice president, paid for such things as invitations to the reception, hors d'oeuvres, a band, and the Coors beer that was served.

The firm where Effi Barry works, JAM Inc., arranged for Coors' funding of the reception. A JAM spokeswoman said Coors had approached the Black Caucus Foundation seeking to sponsor one of the weekend's official functions, but was turned down. She declined to say how much the Barry reception at the Washington Hilton Hotel cost.

In welcoming remarks at the reception, Mayor Barry thanked Coors for sponsoring the affair. "If they Coors had not picked up the tab, we would have had to use taxpayers' money," Barry said.

The AFL-CIO, which is conducting a seven-year nationwide boycott against Coors, has charged that Coors' employment practices discriminated against minorities, women and homosexuals, and violated its employes' civil rights through the use of mandatory lie-detector tests, search and seizure of employe belongings and other practies -- allegations strongly denied by Coors.

Yesterday, local and national union officials said it was wrong for Barry to have allowed Coors to pay for his reception, especially since Barry's strong support of labor and liberal causes conflicts sharply with the staunchly conservative views and policies of the Coors family.

Company president Joseph Coors is a key fund-raiser for President Reagan and has supported and given money to the John Birch Society and the National Right to Work Committee, and was also a co-founder and financial backer of the Mountain States Legal Foundation, a conservative group formerly headed by James Watt, former Department of the Interior secretary.

Joslyn N. Williams, president of the Metropolitan Washington Council, AFL-CIO, the area's largest labor body, said yesterday that letting the Coors company sponsor the reception had the effect of "giving credibility" to the Coors family and its political views. He accused the Coors company of "exploiting workers, women and minorities."

Hotel workers union leader Ron Richardson also criticized the decision, saying the Coors family uses its money "not only to thwart the labor movement, but to fight the civil rights movement -- the kinds of causes most of us believe in."

John E. Mara, secretary-treasurer of the AFL-CIO's Union Label and Service Trades Department, who helps coordinate the boycott, said yesterday that "we do not like the idea of Mayor Barry and Mrs. Barry now embracing Coors. . . . "

Barry said yesterday that allowing Coors to sponsor the reception "in no way" changes his strong support of labor, collective barganing and the rights of workers, women and other minorities. "Sponsorship does not mean agreement" with Coors, Barry said, adding, "but these affairs do cost money."

He said a $60,000 budget to promote the city had already been overspent for the year, and he had directed aides to find private sources to pay for the reception.

Asked about the criticism, Barry replied: "Of course, I'm concerned about the unions being concerned. . . . My view supporting the union movement is clearly known."

Barry noted that last year when Coors attempted to become a sponsor of the first Georgia Avenue Day festival, his administration helped remove the firm as a sponsor. He said aides are preparing a position paper on the Coors controversy for him.

Coors has denied the AFL-CIO's charges and maintains that its policies have been misrepresented by labor. The firm has increased its hiring and promotion of minorities, and recently signed an agreement with a coalition including the NAACP to launch a $325 million, five-year ecomomic development program for minorities.

Effi Barry's duties as vice president for corporate affairs at JAM include working on the firm's program to promote Coors in the Washington area and among minorities nationwide, according to Jeanne Clarke Harris, JAM's president.

Mayor Barry said yesterday that his wife'e employment at JAM and her efforts on behalf of Coors is a separate matter and should not be confused with his views on the firm.

Harris said she approached the mayor's aides about having Coors sponsor the reception and Effi Barry played no role in the matter.

Harris said Coors was turned down for sponsorship of a sanctioned reception by the Black Caucus Foundation because of a speech by Coors chairman William Coors in which he allegedly made derogatory remarks about blacks. Coors has said that the remarks were incorrectly reported.

Union officials, including Williams and aides to AFL-CIO president Lane Kirkland, have also expressed concern that Coors paid for invitations to an Oct. 11 fund-raising dinner for the local chapter of the United Negro College Fund. Effi Barry is the dinner chairwoman.

Harris said Effi Barry was not involved in having Coors become a sponsor and it was a "coincidence" that she is chairwoman of the dinner.