Washington Urban League president John E. Jacob, whose soft-spoken style and low political profile helped transform the organization from the diplomatic corps of the civil rights movement to a depository of information about and programs for Washington's minority communities, has resigned.

Early next year, Jacob, 43, will become executive vice president -- the number two person -- in the National Urban League's New York office, after helping the Washington organization cope with the first years of a new political climate in which former allies are often on opposite sides of the governmental fence.

When Jacob, who left Washington in 1969 and served for five years as director of the San Diego Urban League, replaced Sterling Tucker as Washington league director in 1975, the change was just beginning.

Under a form of limited home rule, power in the District of Columbia was being passed from the hands of appointed officials and congressional overlords to the first elected government in a century -- a government dominated by former civil rights and community activists.

"Nine years ago," Jacob recalled in an interview, "we could deal with black-white issues. We could deal with issues on the grounds of what the system was doing to us and we could usually do that in terms of blacks against whites.

"When I left Washington, we had an appointed government and a certain cast of characters was demonstrating against that government. When I came back, that cast of characters was running the government, and they were people whose commitment could not be challenged on the basis of black against white.

The result has been a former civil rights group required to play a dual role, Jacob said, of being somewhat inside the government because of its ties to the activists now in power, while at the same time being outside of city hall as a community voice.

"One of the interesting things about Marion Barry's election (as mayor) is that he will be open to organizations like ours biting off a piece of the action to improve the community," Jacob said. "The league will have a role of prodding the new government in the direction we think it ought to go based on our contract with the people."

Jacob's appointment as the chief administrative aide to National Urban League president Vernon E. Jordan and the principal manager of a $14 million-a-year organization with 114 chapters was announced last week. The appointment becomes effective Feb. 1.

William W. Barr, chairman of the board of directors of the Washington Urban League, said an acting president will be named until a successor can be found for Jacob. Two vice presidents -- Lillian M. Long and Dorothy J. Sharpe -- will supervise the agency's operations until that selection is made.

Barr said Jacob's major contributions to the league had come through improving its management, increasing its credibility as an advocacy voice and increasing its ability to develop and obtain funds for various programs.

"His effort," Barr said, "has been to stabilize and regroup the programs, to rebuild staff morale and to really set the course to move into the '80s. We feel the league is ready."

During Jacob's presidency, the Washington league's budget has nearly doubled, to about $3 million for 1979, and its membership has increased about 25 percent to around 9,000 members, according to league officials.

One of the most publicized actions undertaken during Jacob's administration was "SOS '76 -- Speak Out for Survival," a random survey of some 1,000 low-income households in the city that forcefully and graphically underscored the problems of the city's poor.

The league used the study to reshape its own program operations, and time and again cited its findings in testimony before various governmental panels. A similar 1978 study has been conducted and should be released before his departure, Jacob said.

Unlike Tucker, who after bringing the city's urban league out of obscurity used the notoriety he had gained as a stepping stone to a appointed and elected office, Jacob dodged elective politics, even though he served on several influential boards and commissions.

"One of the problems the District of Columbia has is that our ambitions are limited to elected politics. Something is wrong with a community when it's that one dimensional," Jacob said. "Somebody has to try to evidence that you don't have to want to be mayor or on the City Council to have a legitimate interest in what happens in the community."