FBI Director Robert Mueller took responsibility Friday for problems over how the FBI used so-called national security letters to obtain sensitive information during terrorism investigations.
"I am the person responsible. I am the person accountable," Mueller told reporters during a news conference.
But despite Mueller's admissions, congressional leaders lashed out, scheduling hearings and calling for further investigation into the matter and calling for restrictions on the USA Patriot Act, which broadened the Justice Department's ability to use national security letters, which are key to terror investigations.
The White House, responding Friday afternoon, said President Bush was briefed on the report last week and "expressed serious concern" over the report, although was relieved that there was no findings of intentional misconduct.
Calling for immediate corrective action, the president stressed the need to go beyond the IG's recommendations with additional measures and directed the Attorney General to give him regular updates, White House spokeswoman Dana Perino said, traveling with the president in Brazil. He did not call for the program to stop, with Perino saying the president believes it is "a critical and effective took in fighting terrorism."
A national security letter allows the FBI to obtain information on individuals from telephone companies, internet service providers, financial institutions and consumer credit companies. The Patriot Act allows FBI field office chiefs to sign off on the letters — primarily used for terror investigations — instead of going through usual channels such as getting a judge's signature or a grand jury subpoena.
Mueller -- who will testify later this month before the Senate Judiciary Committee about the report -- said he stood behind the audit, released to Congress by the Justice Department, which says the FBI improperly used the USA Patriot Act to secretly obtain personal information about people in the United States.
He said he has begun taking measures to correct some of the problems cited. He also said, however, that the national security letters are important parts of terror investigations.
The FBI chief also said he should have provided better training and education to employees over how to handle national security letters, but said "I did not."
And, "I should have introduced internal controls and additional levels of review," which he also said he failed to do.
Mueller noted that none of the findings "constituted criminal conduct," and said that the report also was a positive result of good congressional oversight.
"This process, as it should be, is a way to ensure appropriate oversight into the way in how we use this critical tool," Mueller said.
The report brought harsh criticism from members of Congress, who said the agency's activity is indicative of a department that has overstepped its boundaries in the wake of the Sept. 11, 2001, terror attacks, giving up personal civil liberties in the name of terror prosecution.
Lawmakers on Friday began calling for higher levels of oversight and lashed out — on both sides of the aisle — at Attorney General Alberto Gonzales.
"I am very concerned that the FBI has so badly misused national security letters," said Sen. Arlen Specter, R-Pa., top Republican on the Senate Judiciary Committee that oversees the FBI.
Sen. Russ Feingold, D-Wis., another member on the judiciary panel, said the report "proves that 'trust us' doesn't cut it."
"The law is the law and Attorney General Gonzalez has a responsibility to ensure that the law is enforced efficiently and effectively. It is also paramount that if the Justice Department is going to enforce the law, it must follow it as well. With regards to National Security Letters, there was a major failure by Justice to uphold the law," said Rep. Pete Hoekstra, R-Mich., in a statement released by his office. Hoekstra is the top Republican on the House Intelligence Committee.
And saying he would hold hearings on the lapses, House Intelligence Committee Chairman Silvestre Reyes issued a statement saying "these reports present a highly troubling picture of mismanagement, lack of effective controls, and shoddy recordkeeping of NSLs within the FBI."
The report said that for three years the FBI has underreported to Congress how often it forced businesses to turn over the customer data, the audit found.
FBI agents sometimes demanded the data without proper authorization, according to the 126-page audit by Justice Department Inspector General Glenn A. Fine. At other times, the audit found, the FBI improperly obtained telephone records in non-emergency circumstances.
The audit blames agent error and shoddy record-keeping for the bulk of the problems and did not find any indication of criminal misconduct.
Still, "we believe the improper or illegal uses we found involve serious misuses of national security letter authorities," the audit concludes.
At issue are the security letters, a power outlined in the Patriot Act that the Bush administration pushed through Congress after the Sept. 11, 2001, terror attacks. The letters, or administrative subpoenas, are used in suspected terrorism and espionage cases. They allow the FBI to require telephone companies, Internet service providers, banks, credit bureaus and other businesses to produce highly personal records about their customers or subscribers — without a judge's approval.
About three-fourths of the national security letters were issued for counterterror cases, and the other fourth for spy investigations.
Mueller earlier called Fine's audit "a fair and objective review of the FBI's use of a proven and useful investigative tool."
Fine's annual review is required by Congress, over the objections of the Bush administration.
The audit released Friday found that the number of national security letters issued by the FBI skyrocketed in the years after the Patriot Act became law.
In 2000, for example, the FBI issued an estimated 8,500 letters. By 2003, however, that number jumped to 39,000. It rose again the next year, to about 56,000 letters in 2004, and dropped to approximately 47,000 in 2005.
Over the entire three-year period, the audit found the FBI issued 143,074 national security letters requesting customer data from businesses.
The FBI vastly underreported the numbers. In 2005, the FBI told Congress that its agents in 2003 and 2004 had delivered only 9,254 national security letters seeking e-mail, telephone or financial information on 3,501 U.S. citizens and legal residents over the previous two years.
Additionally, the audit found, the FBI identified 26 possible violations in its use of the national security letters, including failing to get proper authorization, making improper requests under the law and unauthorized collection of telephone or Internet e-mail records.
Of the violations, 22 were caused by FBI errors, while the other four were the result of mistakes made by the firms that received the letters.
The FBI also used so-called "exigent letters," signed by officials at FBI headquarters who were not authorized to sign national security letters, to obtain information. In at least 700 cases, these exigent letters were sent to three telephone companies to get toll billing records and subscriber information.
"In many cases, there was no pending investigation associated with the request at the time the exigent letters were sent," the audit concluded.
The letters inaccurately said the FBI had requested subpoenas for the information requested — "when, in fact, it had not," the audit found.
FOXNews' Greg Simmons and Ian McCaleb and The Associated Press contributed to this report.