Less than a third of the children of Maryland's working parents are receiving day care in licensed facilities, according to a report released today, and children who do receive care in regulated facilities are supervised by people whose average pay is less than half that of teachers in public schools.

The findings are part of a report published by the Maryland Committee for Children Inc., a Baltimore-based group that supports improved day care and better training for day-care providers. In the course of the nine-month study, researchers found that 52,528 children in Maryland were in some form of regulated day care in 1982, although the mothers of 168,054 children aged 5 and under worked outside the home. While the remaining children might be cared for by babysitters, housekeepers or relatives other than the parents, researchers said, some undoubtedly are in illegal, unlicensed facilties.

Researchers found that even licensed facilities pay their employes far less than their counterparts in public elementary schools. In the 1983-84 school year, a day-care teacher earned an average of $10,105, compared to the average $22,942 earned by a public school elementary teacher in Maryland. Family day-care providers, who care for children in their own homes, earned an average of $7,905 that year, less than the poverty limit for a family of four in the state.

"The picture which emerges," the report said, "is a fragmented child-care delivery system which is regulated by a myriad of government agencies, family need for child care far in excess of its availability, limited government subsidies . . . and child-care personnel salaries which are not comparable to others in the field of education."

The quality of day care has drawn increasing attention as more and more mothers join the work force. In 1980, 56 percent of Maryland mothers with children from the ages of 3 to 5 and 47 percent with children under age 3 were in the labor force, according to the study. Compounding the concern in recent months have been reports of child abuse nationwide, both in homes and in day-care centers.

A state government task force has been working on proposals to tighten child abuse laws, and Maryland Gov. Harry Hughes is expected to present the General Assembly this winter with a series of proposals to enhance the lives of children in the state.

But the state's role in providing day care is limited because the government pays for only 8 percent of all day care provided in the state. Thirty-three programs formerly operated by the state were closed after the 1982 Reagan administration budget cuts.

State government officials who attended a briefing on the study yesterday praised the report. Frank Sullivan, director of the day care and special projects division of the Department of Human Resources, said it "may document the end of the infancy of child care. It hasn't been viewed as a major industry, as a major service need."

The 53-page report, which was compiled largely from 1980 census data, also details state and national statistics on family incomes, births, divorces and day-care resources.