Mayor Marion Barry, responding to questions about the high 11.3 percent unemployment rate in the District of Columbia, said last night that the Reagan administration's national policies -- and not Barry -- were to blame.

"I'm not going to take responsibility for the policies of the Reagan administration which add to unemployment," Barry told about 250 people who attended a mayoral candidates' forum sponsored by the Washington Urban League at the Washington Hilton Hotel.

Barry sparred for two hours with six other candidates for mayor, including Democrats Patricia Roberts Harris, Charlene Drew Jarvis and John Ray; Republicans E. Brooke Lee Jr. and James Champagne, and Independent Dennis Sobin.

Harris, who unveiled a job and economic development plan this week that included providing D.C. residents with transportation to available jobs in the area's suburbs, questioned Barry's claim that he had created 50,000 new jobs while the mayor's campaign posters credit him with only 6,000.

"Is it 50,000 or is it 6,000 as it says on the poster?" Harris asked Barry.

"Before I suggested that 6,000 jobs weren't very many jobs to produce in three-and-a-half years, it was a different number."

According to D.C. government figures, 51,227 people have been placed in year-round jobs since Barry took office, including about 7,500 who benefited from locally funded job programs, and the rest who were placed through federally funded programs.

Jarvis, a City Council member from Ward 4, said Harris' proposal for a new economic development corporation to spur private investment and jobs was actually her idea.

"Legislation on which that [Harris' plan] is based I introduced last year. We have had hearings on it and it will be law very soon," said Jarvis, who is chairman of the council's Housing and Economic Development Committee.

Barry stressed that his efforts to encourage economic development were directed throughout the city and would benefit neighborhoods and commercial strips outside the downtown area, including depressed commmercial areas such as 14th Street, Benning Road and Martin Luther King Jr. Avenue.

But Ray, an at-large City Council member, said, "Mr. Barry should be ashamed of himself" for mentioning those depressed areas.

"Nothing has happened in those areas since Mr. Barry took office," said Ray, adding that his first order of business as mayor would be to create a comprehensive development plan for the city.

Champagne asserted that government does not owe anyone a job, but that it should provide equal opportunities for employment through job training, tax incentives for private businesses, apprenticeship programs and courses in public schools that would prepare students for existing jobs.

Lee, defending the Republican Reagan administration, described himself as "your Republican business candidate" who would attract white-collar and blue-collar jobs to D.C. and create enterprise zones in depressed areas of the city.

Sobin said he would emphasize job training and would work closely with the public schools and the University of the District of Columbia.

In response to a question, Barry emphatically ruled out a one-on-one debate with Harris, his chief Democratic rival, before the Sept. 14 primary.

Barry said such a debate would be unfair to Ray and Jarvis, the other two Democrats in the race who have appeared with him at a majority of the 75 candidates' forums.

"There's one person who's usually absent from those forums and it's Mrs. Harris," Barry said.