Nancy Reagan, whose controversial practice of accepting free designer clothes was disclosed a month ago, returned an expensive handbag and belt to their designer, Judith Leiber, six months after they had been sent to her as birthday gifts.

Leiber said yesterday in a telephone interview from Florence, Italy, that the handbag and belt were returned to her last month and that a note from the first lady accompanied them. In it she said that she was not wearing them and felt that someone else might use them more.

Leiber's bags, including a $1,600 alligator bag Mrs. Reagan wore with her inaugural outfit, range in price from several hundred dollars to several thousand.

The White House would not confirm whether or not the return of Leiber's birthday gifts was part of a new policy. Sheila Tate, the first lady's press secretary, said she was unaware of the specific return.

Tate did say Mrs. Reagan returned the borrowed Bulgari jewels she had worn to the wedding of Prince Charles and Lady Diana in London, shortly after she got home last summer. The value of the loaned diamonds, rubies, pearls and sapphires was estimated at hundreds of thousands of dollars.

The return of the Leiber gifts was the latest development concerning Mrs. Reagan's practice of accepting free apparel and accessories from top American designers. When she first announced it last month, she said they were "loans" and that some would be donated to American museums.

Tate quoted Mrs. Reagan as saying yesterday of the controversy over the project, "I'm sorry See GIFTS, C9, Col. 1 GIFTS, From C1 that what I've been trying to do has been misinterpreted."

The Associated Press, in a story by Maureen Santini, reported yesterday that White House aides had been surprised by Mrs. Reagan's disclosure of free designer clothes. "Worried White House aides," the story said, conceived the museum project "to minimize the public relations damage the issue could cause."

The AP said that the first lady revealed her practice of accepting the clothes during discussions of the White House gift policy following disclosures that then-national security adviser Richard V. Allen had accepted two wristwatches from Japanese friends. Mrs. Reagan reportedly wondered whether clothes she had been given by designers would fall in the same category.

Allen, who subsequently resigned, had "no comment" yesterday on the report that his troubles triggered Nancy Reagan's first disclosure to aides of her free clothes.

The AP quoted an unidentified administration official as saying, "I think it's fair to say that we saw it as a potential public relations problem." The official added that it was a way "to minimize any PR problem because it was a way to devote those clothes to a bona fide or beneficial sort of public use."

Tate, responding to the report yesterday, said it had been Mrs. Reagan's intention all along to give clothes to museums and that she had done so before moving to the White House.

One administration official, who did not want to be identified, said yesterday he doubted that the Allen issue sparked the first lady's newest project involving her clothes. He raised the question of whether the Reagans had been concerned about how to deal with the free clothes on their financial disclosure form, which is due in May.

High-ranking government officials and their spouses, under the 1978 Ethics in Government Act, are required to report gifts valued at more than $35 as well as loans and other financial liabilities exceeding $10,000.

Just how the law affects gifts of clothes to the first lady is unclear. The White House contends that clothes Mrs. Reagan passes on to museums are loans. Fred F. Fielding, White House counsel, has said previously, "We probably would not have to report that sort of an item but we will make notice of that someplace on the reporting form to comply with the spirit of the law."

Yesterday Fielding said the owner decides whether an item is a gift or a loan to the first lady.

Fielding said it had been Mrs. Reagan's idea to donate gowns to museums and it was unrelated "to the tax aspects."

While the first lady's free clothes have been the focus of recent attention, there are items in the president's closet, too, which could raise similar questions.

Last August, the president received four pairs of handcrafted boots, estimated to be worth $1,000 per pair, from the Tony Lama Boot Co. of El Paso, Tex. The president has worn them on several occasions.

Last night, Fielding said the Lama boots will be reported.