Federal, state and local governments increasingly are turning to private firms to build or manage institutions for work-release prisoners, illegal aliens and juvenile delinquents, according to a National Institute of Justice study released yesterday.

No prisons have been constructed or managed by private firms, the study said, although a private firm in Texas is planning a local jail that also would be used for illegal aliens.

Prisons are institutions in which persons convicted of crimes serve sentences; jails are institutions in which persons charged with crimes await trial or serve short sentences.

"Corrections departments have long relied on private vendors to furnish specific institutional services or to operate after-care facilities and programs," said James K. Stewart, director of the National Institute of Justice. "But they now are turning to the private sector for help in financing new construction and in managing primary-confinement facilities."

Stewart said the trend has resulted from overcrowding and the escalating costs of prisons and jails.

Allowing private firms to manage such facilities has been controversial within the corrections field. The National Sheriff's Association opposes the trend, while the American Correctional Association has said it is willing to give private firms a chance.

The study showed that 28 states pay private firms to operate halfway houses, work-release centers and prerelease centers for those with lenient sentences or who have served most of their sentences. States that employ private firms most frequently are California, Massachusetts, Michigan, New York, Ohio, Texas and Washington.

In addition, private firms operate hundreds of state residential programs for 10,712 juvenile delinquents nationwide, the study said.

The Immigration and Naturalization Service has issued four contracts to private firms to build facilities for illegal aliens awaiting deportation, the study said. The INS plans to award five more such contracts.

The study also said private firms have constructed jails for two states -- Alaska and Ohio -- under a lease/purchase agreement in which the state buys the jail from the firm over time. Ordinarily, governments finance jail construction with general-obligation bonds that require voter approval. The lease/purchase agreement allows governments to "circumvent" the "referenda requirements of general-obligation bonds," the study said.

"Because no voter approval is required, lease/purchase agreements undeniably reduce citizen participation in corrections policy," the study said.