Over the last five years, about 25,000 people in the District of Columbia were forced to move from their homes and neighborhoods because of condominium conversions, renovations and increased housing costs, according to a new, comprehensive city government study.

If present trends continue, the study predicts, another 75,000 people could be displaced in the next four years.

The study by the D.C. Rental Accommodations Office is the first major examination of the effects of the transformation once decaying, and still riot-scarred, neighborhoods in Washington's inner city.

"This process is remarkable because of the speed with which it is occurring, because of the lack of government involvement and because it is taking place in neighborhoods which only a decade ago were suffering from blight and disinvestment," the report stated.

The change has often pitted elderly or poor longtime black residents against young, affluent white professionals in a struggle for dilapidated but gracefully designed inner-city houses.

There was no information in the study on where displaced families move, but other surveys have indicated that many double up in apartments and homes of relatives and friends nearby, and about one-fourth move to suburban Maryland and Virginia.

The displacement phenomenon has prompted one of the most emotionally charged issues in the politics of this city's new, black home rule government. With black persons displaced, some elected leaders and black businessmen see the change as being part of an elaborate scheme -- The Plan, it is called -- to return political control to whites.

The report by the Rental Accommodations Office offers other explanations for the trend.

It is the large post-World War II "baby-boom" generation, now come of home-buying age, that has increased demand for Washington real estate, the study said. The demand is coming more from young adults moving here from elsewhere in the country than from suburbanites moving to the city. Their arrival has come at a time when the city has seen a decline in the number of rental apartments and houses, thereby adding to pressures for housing.

The study was conducted and prepared by employes and a special temporary staff at the city's Rental Accommodations Office -- more than 35 people who the report said served as a "human computer" in searching through files on evictions, condominium conversions, real estate sales prices and building permits in addition to drawing upon information from other reports and census statistics.

The report says that the displacement problem is concentrated in the central sections of the city, primarily in Wards 1, 2 and 6, which contain such neighborhoods as Adams-Morgan, Dupont Circle, Capitol Hill and Shaw.

D.C. City Council member David Clarke (D-Ward 1) had no trouble agreeing yesterday that displacement is a major problem in the communities he represents. Speculation has taken a "drastic" hold there, he added.

"How long do we have to document it?" Clarke asked. "I've been screaming about this since I came in here. You can't take a walk through my ward or go to a restaurant without knowing that it is happening."

Dorothy Kennison, the city's rent administrator, declined to comment yesterday on the information in the draft report. "I don't consider it final," Kennison said. "I haven't officially released it.