Policy-makers for the United Presbyterian Church this week reendorsed a controversial requirement that local churches include women on their lay decision-making boards.

The rule has caused considerable dissension in conservative congregations of the 2.5 million-member denimination since it was adopted last year. More than a score of congregations have voted since then to leave the denomination.

This year's General Assembly of the church, meeting in Detroit, reaffirmed the rule that local churches must elect women along with men as ruling elders on sessions, as the governing units of the congregations are called.

In a compromise, the General Assembly ruled that dissenting congregations could be exempted by a three-fourths vote of approval by the local presbytery. Grounds for such a waiver were not specified.

The ordination of women to the ministry, which the church has permitted for 25 years, was not involved in the current controversy.

In another action to discourage dissenting congregations from leaving, the General Assembly voted to tighten its constitution to specify that the property of a local congregation is held in trust for the church as a whole.

Since that move would involve a constitutional change it must be ratified by a majority of the 152 local presbyteries and thus would not take effect for another year.

The action was proposed by the church's top leadership because of a Supreme Court ruling that in cases involving churches that do not spell out the control of property, "neutral principles of law" could be used to determine ownership.

The action would put in legal language what always has been an assumption in the denomination.

In other actions, the delegates, or commissioners said the costs of their nine-day annual gathering, estimated at 800,000 and rising each year, should be cut. But at the same time they rejected a proposal to switch from annual to biennial meetings.

Among mainline denominations, only the Presbyterians and the Southern Baptists meet each year.

Delegates rejected a proposal to withdraw the church's support from the World Council of Churches' Program to Combat Racism, which has come under fire for giving aid to rebel groups in southern Africa. One recipient of such aid, Robert Mugabe of Zimbabwe, is not president of that country.

The Rev. Charles A. Hammon, 46, of West Lafayette, Ind., was elected moderator of the church for the coming year, the top elective post in the denomination.

In his annual report, William P. Thompson, stated clerk, pointed out that the net membership loss of 43,003 persons in 1979 was the smallest decline in a decade. The denomination posted a gain of 67 new congregations.