Nancy Reagan's decision to donate to American museums some of the clothes "loaned" to her by top designers has drawn praise and stirred criticism even before the first package containing 12 dresses and a stole has been opened.

The Nancy Reagan plan "is being done to encourage the American fashion industry," according to Sheila Tate, press secretary to the first lady. The donations will provide no tax advantage to Mrs. Reagan since she has not owned the clothes.

"You have to consider that fashion is a very important industry, the third largest in the country by some counts and the largest in New York, paying more taxes than any other," says New York designer Halston. "It is the first lady's responsibility to support this industry and she has done a terrific job. She puts forth a genuine effort with a change of silhouette, and a change of decollete."

Halston, who sold many hats to Jackie Kennedy through Bergdorf-Goodman while the Kennedys were in the White House, is not against loans to the first lady of clothes that will eventually end up in museums. "It depends on what it is. Something important like an inaugural dress or dress worn to a state dinner becomes a historical document, interesting to a museum or an institution. These are historical documents that shouldn't be lost."

"Anything that helps the fashion industry that employs so many people in this country has got to be good," says Val Cook, vice president of the Chevy Chase boutique Saks-Jandel. "She is the best model this country has ever had in terms of promoting what we do well. Since she goes to the best designers, she presents a worthy model to all women to look well."

But at least one designer disagrees with Mrs. Reagan's wearing and donating free clothes.

"Eleanor Roosevelt and Bess Truman were great first ladies and their appearance was secondary," says Geoffrey Beene, whose clothes have been worn often in the White House. Beene says that if asked, he would make a dress for Mrs. Reagan "to do with as she pleases, even burn it." But the plan of wearing and donating borrowed clothes has "overtones of a commercial."

Sheldon Cohen, a Democrat and former commissioner of the Internal Revenue Service, objects to the plan not as a tax scheme but as a matter of ethics. "It is using one's office for personal gain," he says.

An IRS agent is forbidden from even taking a lunch, Cohen points out. "Is a dress less than a lunch?" he asks.

"These people don't understand that maybe you shouldn't do something like this. It is more a question of taste than anything else. It smacks of favoritism and gives the appearance of privilege to a certain group. You can bet your life that the designer who provides the gowns will be invited to the White House regularly, be put on some advisory group and maybe be part of a delegation to the Vatican," he says, though he notes that some may be deserving of those roles.

Fred Fielding, the White House counsel, doesn't agree. "I don't think that any designer who has loaned dresses to the first lady has done so with any such motivation," he said. "There is nothing unethical about accepting a gift of clothes unless it would create a conflict of interest."

The Beaded Dress

Just which first ladies have accepted clothing as gifts in the past is without documentation. The requirement for reporting personal gifts only started when the Ethics in Government Act became effective in 1978, Fielding pointed out.

This week Nancy Reagan selected the outfits to be donated, wrote up labels that included information about the functions to which they were worn and had them dispatched to Ann Keagy, chairwoman of the Parsons School of Design fashion design department in New York. Keagy, who will administer the program, has been so busy with registration for the new semester she has yet to open the package.

"What prompted the giving was a desire to take an incredible interest in fashion that has existed as long as I have been with her, to turn it to productive advantage of one of the nation's biggest and most important industries," said Tate.

Mrs. Reagan arrived at the mechanism for the clothing plan, according to Tate, in December following enthusiastic support from the fashion industry when she proposed a first lady's fellowship, privately funded, to study American fashion at the Smithsonian. She announced the study project when she passed along her white-beaded inaugural ball gown, lent to her by designer Jimmy Galanos, for permanent exhibit in the First Ladies Hall of the Museum of American History.

Pins and Needles

"She has certainly given the fashion industry a shot in the arm," says Mary Hoyt, who was press secretary to Rosalynn Carter. "But the emphasis on the unusual acquisition and disposition of her clothes could be perceived as a cold and inappropriate priority in these times."

"It is not a good idea because Mrs. Reagan seems kind of remote and special because, among other things, of the expensive clothes she wears. This makes her more remote -- a woman who doesn't even wear her own clothes," says Betty Furness, former special assistant to President Johnson for consumer affairs. "I have a mental image of Mrs. Reagan, in this circumstance, as a paper doll. We'll take out our paper doll dress and put it on with tabs today.

"With the country in the kind of troubles it is in today for the first lady to be doing this thing . . . it is magic time . . . who wouldn't like to be borrowing clothes. But it makes her seem that much more unreal."

Not since Jacqueline Onassis has the White House had a first lady so interested and skilled in style. Both well groomed, both collectors of clothes, both near model size, both are given high marks from fashion designers, manufacturers and fashion supporters around the world. And with the American fashion business downturn at the moment and the industry's push for gains in the international market, Mrs. Reagan as a showcase for American clothes has an enhanced role, many designers and retailers say.

"I think historically it would be important to the history of fashion, both as an art and an industry for museum collections," said Deeda Blair, whose own clothes have been added to several museum collections. "It is very important that they go to small museums across the country. Who knows where the talent in the years ahead will come from?"

Keagy, speaking of the museums across the country she has selected to receive the clothes, said, "They are the only places a student has to go to see quality garments. In a department store they are chased. Even if they linger in front of a store window they are chased."

"Forgive me," Furness said, "but who beyond Galanos is making clothes all that well today. The dressmaking details students can learn from aren't being done anymore except by Galanos." Adds Furness, who has worn designer clothes for years: "Clothes are so different today. You don't have to go to a museum to see how Calvin Klein's clothes are made. Sewing lesson number two will show you that."

Mamie Eisenhower's Hat

Robert Riley, former curator of costume at the Brooklyn Museum and director emeritus of the Edward D. Blum Laboratory at the Fashion Institute of Technology, is upset by Mrs. Reagan's plan.

"It is quite a gag, isn't it? But I would take a look at the gift horse," he said. "There is an interest in having something worn by the first lady," said Riley, who had acquired a Sally Victor hat worn to the inauguration by Mamie Eisenhower inspired by Japanese armor in the museum collection.

But Riley calls Mrs. Reagan's acceptance of "loaned" clothing "a terrible piece of chutzpah . . . It really makes me sick."

Said a museum official, who declined to be identified: "Just because Nancy Reagan wore a garment doesn't make it museum quality." The curator would rather the selection be made on the "quality of the garment than the quality of the wearer."

Meanwhile, Bess Abell, former social secretary to Lady Bird Johnson and chief of staff for Joan Mondale, quipped: "I just wish I was size six. I'd open my own museum."