The Washington area has a persistent and growing underclass of poor families who are concentrated in the District and headed by single black women with several children, less than a high school education and no job, according to a report for release today by the Greater Washington Research Center.

As a result, one-third of the city's children are born into poverty from which there is virtually no escape because the unemployment rate for young black men grew dramatically during the 1970s, the report said.

"The future is grim for significant numbers of black youngsters in the nation's capital . . . ," said a summary of the report, the first comprehensive look at poverty in the area in several years.

*One of three black children in the District is poor and national research indicates these children -- the current figure is about 36,000 -- are likely remain so for more than 10 years.

*Half the city's poor live in black female-headed families, and the report says that the traditional methods for escaping poverty -- education, employment or marriage -- are less likely to be available to these women.

*Black female heads of households receive the lowest rates of pay and have more children and less education than any other population group in the area, the study found.

"Many of these people -- including many children -- are lost to the economic mainstream for many years," said R. Robert Linowes, a well-known area zoning attorney and chairman of the board of trustees of the center, an independent organization that analyzes the people, economy and government services in the Washington area.

"With publication of this paper, we . . . invite residents of the Washington area to take the first step: to acknowledge that this rarely discussed problem does exist," Linowes said at a press briefing on Friday. "Then we need to take the second step: to devise solutions."

James O. Gibson, president of the Eugene and Agnes E. Meyer Foundation, added, "There has not been a disciplined attempt in this community . . . to attempt to draw a very accurate local picture of the poor.

"This is a first effort," Gibson said. "Its primary importance is that we must approach this problem in a disciplined and comprehensive fashion, or the signs indicate the problem will continue."

After looking at poverty areawide, the report focused on poor black city residents because they made up a disproportionately large number of the poor. Nearly one in five city residents is poor compared with about one in 15 in the suburbs. In addition, 17 percent of blacks are poor compared with 5 percent of nonblacks.

Because the city's poverty rate soars above the suburban rate, the District's Department of Human Services paid for research in the report comparing poverty in the District with poverty in six cities of comparable size (Atlanta, Baltimore, Boston, Cleveland, Dallas and Oakland). The District has the lowest percentage of black households in the bottom-income brackets and the highest percentage of black households in the top-income group when compared with other cities, the report said.

The center's study focused on the persistently poor, those people who remain in poverty for years. The only way out of poverty for these families appears to be through direct income support, concluded Joan Maxwell, the report's author. But Maxwell stopped short of making any recommendations, calling poverty "a very complex problem" that requires political decisions in order to devise solutions.

Over the long term, Maxwell suggests, the single most effective way the District could reduce its poor black population is to increase the educational levels of its low-income residents, especially the young.

Using data from the 1970 and 1980 censuses and the 1980 official U.S. poverty level for a family of four persons of $8,414, the report found:

*Poverty rates among black residents of the District were three times the areawide overall average and 5 1/2 times the rate for whites in the suburbs.

*More than half of the District's poor black heads of households of working age (24 to 64) had not completed high school. Nearly two-thirds of all black female family heads in poverty of the same age had not completed high school.

*Black women with high school degrees earned only 73 cents for each dollar earned by their white male counterparts. (For black men, the rate was 81 cents; for white women, 76 cents.)

*The percentage of unemployed black adult males jumped from 27 to 41 percent during the 1970s, so that, by 1980, one out of four black males in their late twenties and one out of five black men in their thirties were not working at all.

*The percentage of adult men working full time has dropped, but the sharpest decline has been among black adult men where the rate of those in full-time jobs has fallen by one-third -- from 62 to 39 percent.

The report suggests a correlation between the rise in black male unemployment and the significant increase in black female-headed households.

"Of course there is a relationship," said Joyce Ladner, professor of social work at Howard University. "Who are these women to marry? If a man can't support a family, in America he is considered to be a disfunctional marriage mate.

"My concern is that none of these problems can be settled at the level of self-help," Ladner warned. "What we are dealing with first and foremost are major shifts in the economic market and blacks being disproportionately poor . . . . We need to get serious and deal with prevention . . . or the welfare rolls will continue to grow."

Audrey Rowe, the city's commissioner of social services, said the Department of Human Services hopes to learn from the study "how to assist families from moving from dependence to independence."

Rowe said she will see that the report is handed over to the mayor immediately and distributed throughout the District government.

"We have seen a significant increase in families coming into the adoption system and child services" because mothers could not afford to keep their children, said Rowe, adding that the Human Services Department is asking for a 25 percent increase in its budget for next year.