A broad spectrum of Washington's religious leaders vented its outrage yesterday over proposed regulations that would drastically limit tax exemption for churches and vowed to take the city to court if the measures are adopted.

In a press conference coordinated by the Interfaith Conference, the Protestant, Catholic and Jewish leaders and lay persons charged that the proposed legislation would boomerang by wiping out valuable community service programs.

The proposals under attack would define the function of a church solely in terms of "religious worship." Exemption from real estate taxes would be denied religious institutions that fail to use 60 percent of their floor space for worship for more than 30 percent of the time the facility is in use. Church leaders said yesterday the proposal would affect most of the churches and synagogues in the District.

"We encourage and provide safe places for the recreation, education and life development of our youth," said Onra Dillard, lay leader representing the 27 United Church of Christ congregations in the area. "We provide . . . for the indigent . . . for the elderly and the worn."

"A modern Pharoah is asking us . . . to make bricks without straw," declared Bishop John Hurst Adams of the African Methodist Episcopal Church. Adams, vice president of the Interfaith Conference, a group that brings together Protestant, Catholic, Jewish and Muslim leaders, promised that if the religious community is unsuccessful in getting the controversial regulations withdrawn, "we will seek legal relief."

Adams also called on "people of faith" to join with religious leaders in a prayer protest at 10 a.m. Thursday at the Municipal Building "where we will pray for the wisdom and guidance of our city officials."

The protest will coincide with the first of three "public round tables" that the city government arranged, after bitter complaints from nonprofit groups last month when the proposed changes were disclosed. Initially, the new law was slated to take effect Feb. l, only 10 days after publication in the D.C. Register and without public hearings.

After the outcry, the deadline was extended. But some religious leaders remain critical of the arrangements for the hearings, to be held in the Police Line Up Room, which seats about 80 people. Representatives of institutions wishing to testify were required to submit their written statement by Feb. l3.

The Rev. John V. O'Connor of the Washington Roman Catholic archdiocese and Rabbi Sidney H. Schwarz, head of the Jewish Community Council, registered concern that the proposed regulations would penalize some of their institutions that function across District lines into surrounding counties.

Several speakers challenged the constitutionality of the proposed regulations yesterday. "The idea that the state can dictate what constitutes religious worship, devotion, piety, duty and activity is unquestionably prohibited by the Constitution . . . and is at complete odds with" the principle of church-state separation, said Dillard.

Although there can be abuses of First Amendment guarantees of church-state separation, Bishop Adams said, "If you're going to live in society, you're going to have to put up with some foolishness. But the policing of religion is not the business of government."