The report by Justice Department Inspector General Glenn Fine said the bureau's processes are inefficient and untimely, CNN said. Fine's report said the FBI system relies on outdated technology and offers little assurance that significant information about potential immigrants is being collected and shared with appropriate authorities.
The report cited "limited supervision and training, and inadequate quality control measures" as reasons for the deficiencies.
The FBI searches paper files in its field offices, a method that adds to massive backlogs of immigration applications and petitions for citizenship and services, the report said.
FBI spokesman John Miller told CNN the growing backlog is a result of added demands on the process following the Sept. 11, 2001, attacks.
Miller said the Immigration and Naturalization Service asked the FBI "to 'rerun' 2.7 million names through a more in-depth name check process" following the terrorist attacks.
"This unexpected deluge of immigration-related name checks overwhelmed existing resources," he said. "Corrective actions implemented over several years have improved the (National Name Check Program's) operations, resulting in record numbers of completed name checks and a reduced backlog."