Episcopal Bishop John T. Walker and Roman Catholic Archbishop James A. Hickey have pledged "a new level of collaboration and cooperation" of their two churches in a move to revitalize efforts for Christian unity.

The two prelates will exchange pulpits this month to dramatize the unity appeal.The exchange is the first in the history of the two churches here.

Tomorrow morning at 10:30, Walker will preach as Hickey's guest at the service of morning prayer at the National Shrine of the Immaculate Conception. The following Sunday, Walker will welcome Hickey at the 11 a.m. service at the Washington Cathedral.

While Hickey's predecssor, Cardinal William W. Baum, has preached at the Washington Cathedral, Walker has never before preached at either the Shrine or St. Matthew's Cathedral, which is the cathedral of the Catholic archdiocese.

In their joint statement, the two leaders emphasized that the exchange of pulpits was not "merely perfunctory observances of the annual week of prayer for Christian unity," which is observed nationally by many churches around the world in late January, but signaled new efforts for unity.

The "new level of collaboration and cooperation," they pledged, would include support for "new forms of responsible ecumenical activity," both at the level of theological discussion and in "joint statements and actions that promote social justice and human welfare in the light of the gospel of Christ."

They termed the many divisions within Christendom "a scandal" and challenged the members of their own two communion and Christians generally to join in renewed efforts for unity. "It would be a sin against the church for anyone at any level to work against that unity," they said.

Christian unity efforts received a major boost from the Second Vatican Council 20 years ago, but have sagged somewhat in recent years as churches have been increasingly preoccupied with internal issues and problems of survival.