WASHINGTON, Oct 24: Previously classified documents released on Monday show that the FBI has conducted clandestine surveillance on US citizens and legal residents for as long as 18 months at a time without proper paperwork or oversight.

Some of the violations found in the documents included — Improper searches and seizures of bank records. — Violation of bank privacy statutes. — Improper collection of e-mails after warrants had expired.

FBI officials, however, say that most of the violations were simply administrative errors.

A private US citizen, David Sobel of the Electronic Privacy Information Center, sued FBI to acquire records of its clandestine surveillance programme.

In a letter sent on Monday to the Senate Judiciary Committee, Mr Sobel and other EPIC officials argue that the documents show how little Congress and the public know about the use of clandestine surveillance by the FBI and other agencies. The group advocates legislation requiring the attorney general to report violations to the Senate.

The documents, the letter says, “suggest that there may be at least thirteen instances of unlawful intelligence investigations that were never disclosed to Congress.”

Mr Sobel, who leaked the story to Washington Post a day before the papers were released, discovered the FBI has conducted surveillance in several cases without authorisation or oversight. The records focus on 13 cases from 2002 to 2004, and are revealed at a time when the US Congress is debating the controversial Patriot Act to see if it has given too much power to government agencies.

Records turned over as part of a Freedom of Information Act lawsuit also indicate that the FBI has investigated hundreds of potential violations related to its use of secret surveillance operations, which have been stepped up dramatically since the Sept 11, 2001, attacks but are largely hidden from public view.

In one case, FBI agents kept an unidentified target under surveillance for at least five years — including more than 15 months without notifying Justice Department lawyers after the subject had moved from New York to Detroit.

In other cases, agents obtained e-mails after a warrant expired, seized bank records without proper authority and conducted an improper “unconsented physical search,” the documents show.

Although heavily censored, the documents provide a rare glimpse into the world of US domestic spying, which is governed by a secret court and overseen by a presidential board that does not publicize its deliberations. “We’re seeing what might be the tip of the iceberg at the FBI and across the intelligence community,” Mr Sobel told the Post. “It indicates that the existing mechanisms do not appear adequate to prevent abuses or to ensure the public that abuses that are identified are treated seriously and remedied.”

The documents focus on 13 cases from 2002 to 2004 that were referred to the Intelligence Oversight Board, an arm of the President’s Foreign Intelligence Advisory Board that is charged with examining violations of the laws and directives governing clandestine surveillance. Case numbers on the documents indicate that a minimum of 287 potential violations were identified by the FBI during those three years, but the actual number is certainly higher because the records are incomplete.

FBI officials declined to say how many alleged violations they have identified or how many were found to be serious enough to refer to the oversight board.

Most such cases involve powers granted under the Foreign Intelligence Surveillance Act, which governs the use of secret warrants, wiretaps and other methods as part of investigations of agents of foreign powers or terrorist groups. The threshold for such surveillance is lower than for traditional criminal warrants.

A recent administration report to Congress showed that more than 1,700 new cases were opened by the court last year,

In several of the cases outlined in the documents, FBI agents failed to file annual updates on ongoing surveillance, as required by Justice Department guidelines and presidential directives, and which allow Justice Department’s lawyers to monitor the progress of a case.

Others included a violation of bank privacy statutes and an improper physical search, though the details of the transgressions are edited out. At least two others involve e-mails that were improperly collected after the authority to do so had expired.

Some of the case details provide a rare peek into the world of FBI counterintelligence. In 2002, for example, the Pittsburgh field office opened a preliminary inquiry on a person to “determine his/her suitability as an asset for foreign counterintelligence matters” — in other words, to become an informant. The violation occurred when the agent failed to extend the inquiry while maintaining contact with the potential asset, the documents show.