Complaints from substitute teachers in Montgomery County schools have sparked an investigation into cuts in the substitutes' pay that were made to free funds for a salary increase for fulltime teachers.

The county board of education this week asked Superintendent Charles M. Bernardo to study whether the pay cuts could be restored. The probe was ordered after board members heard arguments thatthe cuts were unfair from representatives of the Maryland Association of Substitute Teachers (MAST).

The organization was founded last month after the board reduced the daily pay for the county's 2,880 substitute teachers from $34.50 to $30. The savings of $494,000 was to be used to help cover a 6 per cent pay raise for fulltime teachers.

The county council has approved a 4.2 per cent cost of living increase for the regular teachers but school employees negotiated a 6 per cent raise with the school system. The board of education had to find money to cover the difference.

Members of the substitutes' group told the board of education this week that the pay cut is only the latest in a series of decreases for substitute teachers.

"How would you like to make 12 cents more (per day) than you earned five years ago? That's what you are asking us," said Martha Cooper, a substitute. "The pay cut given us smacks of ridicule." She was loudly applauded by the audience of about 100 persons.

In the past the board has granted substitutes the same pay increases negotiated for other teachers although the substitutes are not prepared by the Montgomery County Educators Association, the bargaining group for other teachers.

Last year, however, substitutes did not receive a cost of living raise although other teachers did. At the same time, substitutes' working hours were increased from seven to seven and a half hours a day.

In addition, a $46.35 ceiling was placed on the daily amount that subsitutes could earn when they were hired for more than two weeks at a time, cutting the rate they received by as much as $10 a day. In the past substitutes received the same pay as fulltime teachers when they reached the 16th consecutive day of employment; on the 16th day, the fulltime pay became retroactive. When the school system put the ceiling into effect it also did away with the retroactive pay for the first two weeks of consecutive work.

The board this week also asked Bernardo to investigate the fiscal effects of restoring extra pay to substitutes for their total assignments when they are hired for a long period.

Bernardo said his report will be ready next week.

The substitutes' organization also submitted a list of other grievances, including a complaint that they do not earn sick leave, annual leave or retirement benefits and are not compensated at most schools if they report for duty when classes are cancelled because of snow or if two substitute teachers are accidentally hired for the same job on the same day. The group also said that school administrators have not given substitutes support when students become unruly.

More than 300 substitute teachers have joined MAST since it was founded, according to Evelyn Kaplan of White Oak, the spokeswoman. The group has met with representatives of the American Federation of Teachers and was to meet this week with Henry Heller, president of the Montgomery County Educators Association. MAST members also were to decide this week whether to join an established teachers' organization or to remain independent.