The Federal Bureau of Investigation has incorrectly kept nearly 24,000 people on a terrorist watch list on the basis of outdated or sometimes irrelevant information. By the beginning of 2009, the report said, this consolidated government watch list comprised about 400,000 people, recorded as 1.1 million names and aliases, an exponential growth from the days before the attacks of Sept. 11, 2001. The new report, by the office of the Justice Department's inspector general, provides the most authoritative statistical account to date of the problems connected with the list. An earlier report by the inspector general, released in March 2008, looked mainly at flaws in the system, without an emphasis on the number of people caught up in it. The list has long been a target of public criticism, particularly after well-publicized errors in which politicians including Senator Edward M. Kennedy and Representative John Lewis showed up on it. People with names similar to actual terrorists have complained that it can take months to be removed from the list, and civil liberties advocates charge that antiwar protesters, Muslim activists and others have been listed for political reasons. One of the biggest problems identified in the report was the use of outdated information, or material unconnected to terrorism, to keep people on the bureau's own terror watch list, which is incorporated in the consolidated list. The report, examining nearly 69,000 referrals to the F.B.I. list that were either brought or processed by the bureau, found that 35 percent of those people, both Americans and foreigners, remained on the list despite inadequate justification.