Calling the Reagan administration's proposed budget cuts in health programs "imprudent and counterproductive," the head of a major public health group urged yesterday that the funds be taken instead from the Defense Department.

"We want to warn the American public that the president's budget will be harmful to their health," said Stanley Matek, president of the American Public Health Association, who called the reductions "pound foolish and dubiously penny wise."

"There is nothing wise or courageous about taking money from vital health programs and feeding it to the military," said Matek, who maintained that the more than $5 billion proposed to be cut in 1983 from key health programs could easily come out of the "fat in the Defense Department."

The main health cuts are in the Medicare and Medicaid programs, the two largest. Howard Newman, a former Carter administration health official, said that the $2 billion proposed cut in Medicaid assistance to the poor and roughly $3 billion in Medicare for the elderly would inevitably mean a "reduction in services or a transfer of costs" to other sectors.

The health experts also warned of the impact of planned reductions in a host of smaller but in their opinion significant programs providing nutrition for mothers and infants, disease prevention, and family planning that could have long-term health consequences.

They calculated that the cumulative two-year result of 1982 and 1983 cuts, taking inflation into account, would mean more than a 50 percent reduction in maternal and child health and women, infants and children (WIC) feeding programs and a one-quarter reduction at the Centers for Disease Control, which administers programs such as childhood immunization.

"The administration has launched an assault on key health programs which is without precedent, without good justification, and without any evident awareness of the human and economic costs which last year's health cutbacks are already visiting on the public," said Matek, who directs the Orange County Health Planning Council. Health Planning is an area also targeted for elimination by the administration.