A former employe of the Communications Workers of America must be given back pay for a lost promotion because of the union's unjustified, overly protective and stereotyped attitude about the place of women in the union," a federal magistrate ruled yesterday.

U.S. Magistrate Henry H. Kennedy Jr. found that Sally Kraus Marshall had been discriminated against in her job as research assistant at the union by a supervisor who "candidly admitted that during the period covered by this law suit, he preferred working with men to women in professional capacities.

The same supervisor told another CWA female employe that the way to get ahead in the union was to "leave some buttons undone," Magistrate Kennedy found. He also reportedly told an employe that a man received a promotion because he had a family and needed the money more than did the female employe who was up for the same promotion.

"There was other evidence as well which tended to show that Mr. (Ronald) Straw possessed an unprofessional opinion about women workers in general," Kennedy added. Included was the supervisor's alleged reluctance to give field research assignments to women because he and another supervisor did not believe women would be safe or effective given the traditional "hard drinking, tough talking" character of rank and file members, the court opinion said.

Marshall's suit claimed that she was discriminated against because of her sex when she was passed over for a promotion from research assistant to research associate and a man was given the job instead.

Kennedy also found that marshall was discriminated against further when her supervisors began monitoring her performance unusually closely after she filed sex discrimination complaints against them.

Kennedy said the monitoring, reportedly to watch her work habits and to check on her alleged tardiness, was actually done in retaliation for the complaints she had filed.

Marshall, who said in court papers that she felt "forced to resign" after the monitoring began, no longer works for CWA and did not seek restoration of her job there. The exact monetary amount of her back pay awared will be determined later.