The FBI improperly and, in some cases, illegally used USA Patriot Act powers to obtain information about U.S. citizens and residents, a new Justice Department report concluded. The report by Justice Department Inspector General Glenn A. Fine was first reported on the Blotter on ABCNews.com last night. Fine’s office scrutinized the FBI’s use of National Security Letters (NSLs) under the Patriot Act, which expanded their powers. Intended for use in secretive terrorism and espionage cases, the letters allow the FBI to obtain information, such as business records and data on telephone subscribers, without a judge’s consent. Moreover, FBI agents at times requested and received information they were not authorized to obtain under the law, Fine’s report concluded. The report released today paints a picture of widespread misuse of NSLs by FBI agents and confusion about how NSLs are to be issued and recorded. Fine’s office found chronic underreporting by agents about how many NSLs they issued, leading to its conclusion that the total number of NSLs reported by the FBI between 2003 and 2005 — over 143,000 — may be understated by tens of thousands of letters. Click Here for Full Blotter Coverage. As a result, FBI reports to Congress on its use of the secretive powers were inaccurate, the report said. "This report proves that ‘trust us’ doesn’t cut it," said Sen. Russ Feingold, D-Wisc., in a written statement released this morning. Feingold, long an opponent of the FBI’s expansive authorities under the Patriot Act, vowed "full and prompt" investigations into the misuses of NSLs and said he would push for reform. A spokeswoman for Attorney General Alberto Gonzales said last night that Gonzales "has told [FBI Director Robert S. Mueller III] that these past mistakes will not be tolerated and has ordered the FBI and the department to restore accountability and to put in place safeguards to ensure greater oversight and controls over the use of national security letters." In a written statement, a chastened FBI Director Robert S. Mueller III called some of the report’s findings "unacceptable." At a press conference today, Mueller accepted personal responsibility for the FBI’s multiple failures.