Langhorne A. (Tony) Motley, the Reagan administration's departing Latin American policy chief, criticized his clerical and congressional critics last week, saying it is "time to take politics out of the pulpit and the pulpit out of politics."

In what aides said was his last scheduled speech as assistant secretary of state for inter-American affairs, Motley appeared to be responding in part to U.S. church groups that have been among the severest critics of his policies.

"The pulpit is misused when devoted to secular political causes," he said. In Latin America, "Marxists have consciously sought out clergy to serve as window dressing."

Motley added that he was "amazed" that church involvement in politics is rarely debated. "It's a taboo subject. Nobody wants to touch it," he told the Overseas Writers, a journalists' group.

Noting that his office has sent to Congress reports containing a million words during his two years in office, Motley advised its leaders to "sit smartly upon members who seek to conduct foreign policy" without consulting the administration. Although he declined to give names, he apparently was referring to recent visits to Central America by Sens. John F. Kerry (D-Mass.) and Tom Harkin (D-Iowa), who returned with proposals from Nicaragua's Sandinista government.

Motley was asked how things might have been different if the Roman Catholic Church had not gotten involved in El Salvador -- where bishops have led the outcry against human rights violations -- and in Nicaragua -- where administration officials have praised Cardinal Miguel Obando y Bravo as a bulwark against the leftist government.

Motley said he was speaking mostly about U.S. church groups, whose political activity "may have delayed several congressional actions." Referring to much greater economic and military aid proposed for Central America, he said, "Maybe the Jackson plan would have passed six months earlier."

Although churches' political work is sparked by well-meaning people, Motley said, "religious persons should not use the credibility they enjoy to market their personal, philosophical and political beliefs."

Motley, 47, is expected to set up a private consulting firm here when he leaves office, possibly this week. The Senate Foreign Relations Committee has approved the nomination of Elliott Abrams, now assistant secretary of state for human rights, to succeed Motley. Latin Policy Chief Takes Parting Sho