The U.S. Conference of Mayors, warning that Reagan administration spending cutbacks have wiped out much of the progress made in urban areas in recent years, yesterday unveiled a master plan for rebuilding cities that would cost the federal government an additional $49 billion a year.

The study, released a week before the presidential election, blames President Reagan for shifting more and more responsibilities to the cities while reducing critical urban action programs. Since Reagan took office, the report said, a total of $83 billion in spending has been shifted from domestic programs to other areas, including defense and interest payments on the national debt.

"In our view, this is a polite way of saying that urban America should solve its own problems -- that the federal government has higher priorities to attend to," said D.C. Mayor Marion Barry, chairman of the Conference of Mayors panel that drafted the report.

"We would hope that in the closing days of this campaign that both the [political] parties would focus on this issue and make it a major point of discussion," Barry said.

The report offers a 14-point program for assisting major cities, including creation of a National Urban Development Bank that would pump a total of $20 billion in working capital into urban areas over four years. The bank scheme would be similar to the federal Urban Development Action Grant program, which uses federal funds as seed money to encourage private development, but on a much larger scale.

Other proposals include:

*Spending $4 billion a year in federal assistance targeted to economically distressed areas.

*A new national employment and training policy that, in the short run, would reduce unemployment by at least one percentage point and that would restore funds cut in federal spending for jobs.

*A renewed commitment to public and subsidized housing, including rent subsidies for an additional 100,000 units per year and $5 billion a year more for new construction and renovation of moderate income housing.

*Restoration of federal funds cut for social services and day care, as well as a federal takeover of all public assistance programs.

*A return to 1975 levels of funding of federal crime control assistance, which was more than four times the current level of $200 million.

*Long-term, consistent federal support of urban mass transit systems.

The Conference of Mayors opposes the administration's proposal for creating special urban enterprise zones in low-income areas, describing it as "a poor substitute for the massive policy shifts in recent years away from cities."

The $49 billion price tag for the mayors' plan would necessitate significant shifts in federal budget priorities, according to the report, including "adjustment in defense expenditure," an increase in federal taxes and possibly a delay or postponement of federal tax indexing.

Barry said that if future increases in defense spending were limited to the rate of inflation, there would be more than enough to cover the cost of the proposed urban intiatives and to help reduce the federal deficit.

"So it [the study] is not a wish list, it's not a pie-in-the-sky kind of report," Barry said. "It's realistic."

The 420-page report and recommendations, which took two years to complete, was released by Barry at a news conference at the District Building that also was attended by representatives of six groups that endorsed the findings.

Mary Futrell, president of the National Education Association, Carmen Turner, general manager of Metro and a representative of the American Public Transit Association, Rachel Tompkins, executive director of the Children's Defense Fund, and William Lucy, secretary-treasurer of the American Federation of State, County and Municipal Employees (AFSCME) attended the session.

D.C. school board member Bettie Benjamin (Ward 5), president of the Council of the Great City Schools, and Betti Whaley, president of the Washington Urban League, also were present.

The Council of the Great City Schools, a coalition of 35 of the nation's largest urban public schools systems, released another report yesterday assessing the impact of reductions in federal aid to schools during the past four years.

The report concluded that federal funding to inner-city public schools declined by nearly 26 percent per child between fiscal years 1980 and 1984. It also found that total spending on urban schools from all governmental sources declined by nearly 8 percent during the same period.

"These cuts have fallen disproportionately on poor and minority students in the inner cities, exactly the opposite of what should have happened," Benjamin said.

In the District of Columbia, for example, federal support for public schools declined by 39 percent during the past four years, when adjusted for inflation, according to the study.

"This is making it difficult for us to maintain our compensatory education program, our business partnership efforts, our bilingual and vocational programs," Benjamin said. "Already, our in-school youth employment projects have been seriously curtailed."