Leaders of the major religious communions in Maryland, under the banner of the Maryland Interfaith Legislative Committee, have sent a letter to President Reagan sharply criticizing the administration for expanding military spending at the expense of the poor.

"The poor are being deprived of food, clothing, housing and medical care at the same time the government is diverting billions in the expanding defense programs," said the letter signed by 14 Christian and Jewish leaders. "We condemn a defense policy that promotes misery at home."

The religious coalition, which included heads of Roman Catholic, Episcopal and United Methodist Churches in the state, condemned Reagan's budgetary programs for "moving our government away from its role of protecting the economic and social rights of all its people."

The religious leaders challenged the administration's suggestion that people dropped from government programs could be taken care of by private charity.

"Even if all religious groups in Maryland reached their full potential in serving the poor, many people would still receive no help at all," the letter said. "There is no way we can overcome the human suffering inflicted by those losses with our limited resources." The coalition estimated that 286,000 people in Maryland have been affected by U.S. budget cuts enacted to date.