District of Columbia child welfare officials, following a critical review by federal inspectors, announced yesterday a major $1.8 million reorganization of the city's long-troubled system of caring for some 4,000 abused or neglected children who, in many cases, have been set adrift in a disorganized foster-care system.

"Children who come into our system will no longer be lost in the system," said Audrey Rowe, D.C. commissioner of social services, who announced the plan at a news conference.

The reorganization plan includes adding 15 new child welfare social workers, bringing the total to 107; improving training and recruitment of both city workers and prospective foster parents, and increasing the use of private agencies to assist the city in finding suitable foster care and adoption for troubled children.

But the heart of the plan, according to child welfare advocates interviewed yesterday, is what Rowe called "a basic philosophical change" in which the city government will concentrate more on strengthening and reuniting families through "permanency planning" rather than allowing children to be placed frequently in foster homes where they linger for an average of seven years, according to recent studies.

To accomplish this change, the Department of Human Services, which oversees the system, will combine two of its divisions. Child protective workers, who handle abuse and neglect cases, will now be combined with the foster care-adoption division into a new unified Child and Family Services Division.

"It is not just a shuffling of people and paper," Rowe stressed.

The newly unified division will follow a "one worker-one family" policy, in which one social worker will be responsible for supervising a case, said Annie Goodson, head of the DHS family services administration. This contrasts with past practice in which separate divisions assigned social workers to parents and children, sometimes resulting in three or four workers handling one family, she said.

Yesterday's announcement coincides with release of a report yesterday by the U.S. Department of Health and Human Services, which highlighted ongoing deficiencies in child welfare procedures and staffing.

Repeating a criticism that has been voiced for several years, the federal HHS study said a sampling of 400 files showed foster children are frequently "drifting" in care because DHS does not always develop written plans for each child and then review the cases to assure compliance with those plans.

The HHS report said that foster care workers' caseloads in some instances were 117 children, more than 120 percent higher than the recommended standard of 45. The report also said that more than 29 percent of the cases lacked written plans for the child's future care, and 78 percent lacked timely reviews.

The city spends $19 million a year on child welfare. Rowe said the reorganization and other recent improvements will enable the city to collect $6 million in federal reimbursement that becomes available this month under the 1980 federal Adoption Assistance and Child Welfare Act.

DHS has been working for nearly two years to improve child welfare, since a city auditor's report released in 1980 dramatized the chaos of a system in which children frequently bounced between institutions and foster homes for years, with the DHS often losing track of children. As part of its recent effort, DHS this summer began a computerized foster care "tracking system" to assure children are not lost in the system.

Child welfare advocates, who have been highly critical of DHS, welcomed the latest announcement yesterday. "I am glad I lived long enough to see it," said John Theban, longtime director of Family and Child Services of Washington, D.C.

"I am delighted to see this," said Nancy Smith, executive director of the Child Advocacy Center, who said child welfare has been "horribly understaffed" and crisis-oriented, instead of forward-looking in planning a child's future.