President Reagan's inaugural committee has placed an advertisement for 200 nonunion "clean-cut all-American types" to perform free during inaugural week, inciting an uproar among entertainment union leaders throughout the country.

A spokesman for the presidential inaugural committee immediately dismissed the protests as misunderstanding the traditional role of young amateur performers in the inaugural celebrations. But an AFL-CIO spokesman said today there may be a violation of the federal Labor Standards Act and legal action was being considered.

"Our first reaction basically is disbelief," said Sanford Wolff, national executive secretary of the American Federation of Television & Radio Artists. "I think this is the clearest evidence yet that this administration is completely anti-union."

The quarter-page ad, placed at a cost of $255 in the current issue of the trade publication Backstage, asked for nonunion singers and dancers to audition at Radio City Music Hall in New York Jan. 5. "All must be attractive, clean-cut American types," the ad said. Performers were promised free travel and food and lodging "in a government facility or hotel" during the nine-day engagement, but "a fee will not be paid for your participation."

"The whole thing is preposterous," said AFL-CIO spokesman Murray Seeger. He said AFL-CIO secretary-treasurer Thomas R. Donahue had "voiced a strong protest to administration officials" and union attorneys were now considering requests from member unions that they take legal action.

Ken Orsatti, national executive secretary of the Screen Actors Guild, which President Reagan once headed, called the ad "absolutely outrageous." A guild spokeswoman said members from all over the country were calling to express "a great deal of concern."

A White House spokeswoman referred all questions about the ad to the inaugural committee. John Buckley, the committee's deputy press secretary, said "there seems to be a misunderstanding not only about what is historical precedent for inaugurals but what we are trying to do."

The inaugural committee expects to have "more union performers than at any other inaugural in the past," including musicians in nearly 30 bands and orchestras during the Jan. 18-21 weekend of parties and parades, Buckley said.

But inaugural committees, both Republican and Democratic, have always tried to involve high school and college performers in the festivities, Buckley said. When they tried to approach schools directly, "we ran into difficulties because it was a time when many were leaving on Christmas vacation," he said. The ad was placed to ensure there would be enough young performers for planned concerts and the inaugural parade.

Seeger said the request for "clean-cut all-American types" seemed to be a discriminatory code: "It sounds like they want the Mormon Tabernacle Choir." But Buckley called such complaints "complete nonsense . . . All that means is we are looking for people who are friendly, outgoing and pleasant."

Several union leaders complained that the committee neglected the courtesy of even asking entertainment unions if their members might perform for free. Buckley called this "confusing apples and oranges," since the unions represented only professionals and the committee was looking for school-age amateurs.

Buckley said the Saturday audition was held but that he did not know the results. He said 2,000 students from Washington area colleges and high schools are already scheduled to sing Jan. 20 at the Jefferson Memorial and additional hundreds of high school band members will appear in the parade for free, having paid their own expenses. Another 2,000 unpaid volunteers are at work on inaugural preparations.

Alan Eisenberg, executive secretary of the Actors Equity Association, which represents 36,000 stage actors, called the nonunion casting call "an insult to the American performer." He said he will recommend that the association's council formally condemn the inaugural committee.

Seeger said the committee was making money from selling "all kinds of sleazy souvenirs and then has the nerve to ask performers to work free and to specify they be nonunion."

"This flies in the face not only of equal opportunity provisions, but there is a law in the United States that says if you advertise to employ people to work you've got to pay them minimum wage," Wolff said. "You can't discriminate against union members. We can't believe the White House has knowledge of this . . . An inaugural is the kind of event that really transcends politics. People of all political persuasions should be able to participate."