It was the first time the Bush administration has publicly disclosed how often it uses the administrative subpoena known as a National Security Letter, which allows the executive branch of government to obtain records about people in terrorism and espionage investigations without a judge's approval or a grand jury subpoena.
Friday's disclosure was mandated as part of the renewal of the Patriot Act, the administration's sweeping anti-terror law.
The FBI delivered a total of 9,254 NSLs relating to 3,501 people in 2005, according to a report submitted late Friday to Democratic and Republican leaders in the House and Senate. In some cases, the bureau demanded information about one person from several companies.
The numbers from previous years remain classified, officials said.
The department also reported it received a secret court's approval for 155 warrants to examine business records last year under a Patriot Act provision that includes library records. However, Attorney General Alberto Gonzales has said the department has never used the provision to ask for library records.
The number was a significant jump over past use of the warrant for business records. A year ago, Gonzales told Congress there had been 35 warrants approved between November 2003 and April 2005.
The spike is expected to be temporary, however, because the Patriot Act renewal that President Bush signed in March made it easier for authorities to obtain subscriber information on telephone numbers captured through certain wiretaps.
The Foreign Intelligence Surveillance Court, the same panel that signs off on applications for business records warrants, also approved 2,072 special warrants last year for secret wiretaps and searches of suspected terrorists and spies. The record number is more than twice as many as were issued in 2000, the last full year before the terrorist attacks of Sept. 11, 2001.
The FBI security letters have been the subject of legal battles in two federal courts because, until the Patriot Act changes, recipients were barred from telling anyone about them.
Ann Beeson, the associate legal counsel for the American Civil Liberties Union, said the report to Congress "confirms our fear all along that National Security Letters are being used to get the records of thousands of innocent Americans without court approval."
The number disclosed Friday excludes requests for subscriber information, an exception written into the law. It was unclear how many FBI letters were not counted for that reason.
Meanwhile in San Francisco, the Justice Department said it is moving to dismiss a federal lawsuit challenging the Bush administration's secretive domestic wiretapping program.
The lawsuit, brought by the Internet privacy group, Electronic Frontier Foundation, does not include the government.
Instead, it names AT&T, which the San Francisco-based group accuses of colluding with the National Security Agency to make communications on AT&T networks available to the spy agency without warrants.
The government, in a filing here late Friday, said the lawsuit threatens to expose government and military secrets and therefore should be tossed. The administration added that its bid to intervene in the case should not be viewed as a concession that the allegations are true.
As part of its case, the EFF said it obtained documents from a former AT&T technician showing that the NSA is capable of monitoring all communications on AT&T's network, and those documents are under seal. The former technician said the documents detail secret NSA spying rooms and electronic surveillance equipment in AT&T facilities.
Next month, U.S. District Judge Vaughn Walker will hold a hearing on whether they should be divulged publicly.
The EFF lawsuit, alleging AT&T violated U.S. law and its customers' privacy, seeks to stop the surveillance program.
The San Antonio-based telecommunications giant said it follows all applicable laws.