The Reagan administration, pointing to a need for "flexible alternatives" for American workers, has removed a 45-year-old ban against employees working at home in five industries.

Labor Secretary Ann Dore McLaughlin indicated Thursday the ban will be lifted Jan. 9 because "changing demographics demand that we provide employment opportunities that allow workers freedom to choose flexible alternatives, including the ability to work in one's own home."McLaughlin said such flexibility is "a critical element of our effort to create jobs, enhance the quality of work life for American workers and improve our competitive edge in world markets."

The five affected industries were gloves and mittens, embroideries, buttons and buckles, handkerchiefs, and jewelry production that does not involve the use of hazardous processes or materials.

Organized labor has indicated it will challenge the administration's decision in court.

Jay Mazur, president of the International Ladies Garment Workers Union, said the union will seek a coourt injunction on grounds that the repeal of the ban makes the enforcement of wage-and-hour laws virtually impossible.

The work ban was established in 1943 under the new Fair Labor Standards Act. The ban was put in place after a Labor Department investigation found that employees in some industries were working in sweatshop-like conditions where the enforcement of labor regulations was impossible.

McLaughlin said the Labor Department is going to issue tough new policies to assure that federal wage-and-hour laws are not violated after the ban is removed.