The District of Columbia's top planning official suggested yesterday that suburban communities should allow the D.C. government to establish group homes outside the city for some of the several thousand people scheduled for release from the city's mental hospitals and prisons.

"The District should not be expected to solve all the social problems in a vacuum," declared Fred L. Greene, the D.C. planning director. "All of these people should not be stuck in the city. There should be some regional plan to accommodate them."

Greene made his comments in an interview during a conference on area planning sponsored by the National Capital Area Chapter of the American Planning Association.

"Everybody is talking too local and nobody is talking regional, and that's a major problem," Greene remarked.

Later, Arlington County Board member Mary Margaret Whipple, another participant in the symposium, said she recognized the District's problems, but said Arlington already has a large number of group homes for persons discharged from mental institutions in Virginia.

"Each jurisdiction has its own problems," she said. "We still have more to do for our own people."

Under court orders and congressional directives, the District is expected to provide group homes in the next three years for about 2,000 additional people, most of whom will be discharged from St. Elizabeths Hospital for the mentally ill, which is being transferred from the federal government to the D.C. government.

Others are expected to be released from the District's large facilities for juvenile delinquents and the mentally retarded, both of which are in Maryland. In addition, plans to reduce crowding in D.C. prisons call for a major expansion of halfway houses.

Efforts to increase such community-based facilities have encountered sharp opposition in many D.C. neighborhoods, most recently in Georgetown, where the city bought a mansion for $2.9 million to house 24 emotionally disturbed youths.

Greene said yesterday that if the group homes were "spread around" the metropolitan area, "it would lessen the impact in any particular neighborhood" and might reduce local opposition.

The conference at George Washington University was attended by about 100 people, including many local government officials.

Walter A. Scheiber, executive director of the Metropolitan Washington Council of Governments, said the area's major planning successes included the "wedges and corridors" development plan in Montgomery County, in which suburban growth was concentrated along transportation corridors and separated by wedges of open space. He also cited the Pennsylvania Avenue development and the Rosslyn-Ballston corridor plan in Arlington.

But he said planners had not done enough to provide roads linking the suburbs where most area residents now live and work. Scheiber said, "We did not adequately foresee what would happen with the Beltway," which has become a congested "main street" for the area instead of a bypass around Washington for long-distance travelers.