Thousands of Washington juveniles arrested each year are either held too long before trial, unnecessarily separated from their parents or tried by ill-prepared prosecutors because of bad management and inadequate staffing in the office of the corporation council, according to a D.C. Bar report.

The 175-page report alleged "consistent and persistent understaffing, undersupport, and undermanagement and undernourishment" in that section of the office that handles juvenile cases, and said that such shortcomings "must be seen as a policy decision on the part of those who manage that office."

The report said that city lawyers involved in the juvenile cases often fail to attend critical court hearings, plea bargain without written guidelines and are often recruited through a system that invites hiring based on political patronage rather than merit.

While some of the most scathing findings in the report concerned the corporation counsel's office, the document criticized much of the city's entire juvenile system -- either directly or indirectly -- and called on city officials to make appropriate changes.

It noted, for example, that the proportion of arrested youths who are incarcerated before the trial is twice as high as the proporation of adults, and that many of the judges who handle juvenile cases are inadequately prepared to handle child neglect cases. Still, its harshest words concerned the corporation counsel's office.

Various corporation counsels who have served during the last 10 years "apparently have been unwilling to focus on the serious management deficiencies" in the juvenile section, the report said. As a result, the office emphasizes the "putting out of daily fires" and a "catch-as-catch-can" system.

Corporation Counsel Judith W. Rogers said yesterday that virtually all the problems cited by the report stemmed from inadequate financial resources for the office. She said attempts are already under way to make improvements in some of the areas criticized.

"To the extent that the [report] supports us, I welcome it," Rogers said. "All I say is we're dong it, and they should acknowledge it."

The juvenile division of the corporation counsel's office includes about 14 of the 80 lawyers in the office. It handles child abuse and neglect cases as well as prosecution of juvenile offenders. Rogers said that she was unable to fully staff the juvenile division because she must "balance demands that section has" against other section of the corporation counsel's office.

The report was prepared for the bar by the D.C. Court System Study Committee, a 40-member panel of lawyers and lay people. The study began in the spring of 1977 and completed its work this fall. The report was endorsed by the full bar last month.

Its criticisms of city legal opertions comes at a time when city officials and some congressmen are lobbying for the transfer to the local government prosecution of all criminal offenses in the District. Opponents of the transfer city the city's budgetary problems as the reason the city should not take on additional criminal prosecution responsibilities.

The corporation counsel's office -- run on a $4.5 million budget -- acts as the city's attorney general, defending the city in civil lawsuits and prosecuting traffic and other minor offenses. Its primary criminal prosecutions involve virtually all juvenile court cases, since adult crimes are handled by the U.S. attorney's office here.

The report noted the following in its criticism of the corporation counsel's office:

There are insufficient written guidelines on such matters as plea bargains. Much of the written assistance lawyers do receive consists, for example, of "an assortment of memos dealing with a jumble of administrative topics such as work hours and the personal use of telephones."

Prosecutors usually fail to attend disposition hearings -- "the most critical phase of a juvenile proceeding," according to the report -- at which cases are disposed of, leaving the judge and the defense attorney to make the final determination of a juvenile's future.

The corporation counsel's office has a "current ad hoc system" of attorney recruitment that is "an invitation to possible patronage abuse," the report said, but noted that no such actual abuses were found.

The report acknowledged that the corporation counsel's office operated "in a system that imposes many constraints -- too few resources, too many cases, too few judges, and so on. However the corporation counsel . . . must first set its own house in order."