The FBI illegally videotaped suspects, improperly recorded telephone calls and intercepted e-mails without court permission in more than a dozen secret terrorism and intelligence investigations, according to an internal memorandum obtained by a member of Congress.

The errors in the first three months of 2000 were considered so egregious that FBI officials in Washington launched a wholesale review of the agency's use of secret wiretaps and searches, and warned FBI field agents to do a better job of adhering to court orders, according to documents.

The newly disclosed incidents, recounted in a memo provided by the FBI to Rep. William D. Delahunt (D-Mass.), are the latest in a series of FBI mistakes to come to light in connection with the Foreign Intelligence Surveillance Act (FISA), which allows investigators to obtain warrants from a secret court in espionage and counterterrorism cases.

The FISA program is at the center of efforts by the Justice Department since the Sept. 11, 2001, attacks to aggressively monitor suspected terrorists, but past FBI blunders have hindered the reforms. Earlier this year, the secret FISA court, in refusing a request by the Justice Department for broader powers in seeking such warrants, publicly admonished the FBI for misrepresenting facts on more than 75 occasions.

In another instance, also in 2000, technical problems with the FBI's e-mail intercept program formerly known as Carnivore resulted in the capture of communications from people not under investigation.

In the latest case, FBI officials issued an internal memorandum on April 21, 2000, warning of a sudden surge in errors by field agents in administering secret wiretaps obtained under FISA. Among the incidents cited was a case in which telephone conversations continued to be recorded even after the cell phone had been transferred to party not under investigation, and another case in which e-mails were monitored after court permission to do so had been withdrawn.

FBI officials yesterday characterized the incidents as mistakes attributed in part to communication problems between FBI headquarters and the field, and that some agents were disciplined as a result. New procedures dramatically reduced the rate of mistakes, officials said.

"The chance of making a mistake back at that time was far greater than today," said M.E. "Spike" Bowman, FBI deputy general counsel for national security, who estimated an average of 10 errors out of about 1,000 new warrants are reported annually. "This was extremely serious to us, and we went over everything with a fine-tooth comb. . . . FISA is a secret proceeding, and it hardly ever comes to public attention, so it's very important to us that we maintain credibility and confidence."

But Delahunt, a House Judiciary Committee member who requested information about the errors after the Carnivore problems were disclosed in media reports earlier this year, said the incidents underscore the possibility that the FISA process is being abused by law enforcement. The memo's existence was first reported yesterday by the Associated Press.

"If it was unintentional, it demonstrates an incredible level of incompetence," Delahunt said.

Lawmakers last year granted the FBI and Justice greater latitude in using such warrants as part of the antiterrorism USA Patriot Act, but they built in provisions that would require Congress to renew the extra surveillance powers in 2005. Delahunt said the April 2000 memo, which was not disclosed to lawmakers while they were debating the Patriot Act, could cause him and other lawmakers to reconsider extending the new powers.

Sen. Patrick J. Leahy (D-Vt.), chairman of the Senate Judiciary Committee, said Congress should be assured that the problems have been corrected before it grants broader powers to Justice and the FBI.

"Honest mistakes happen in law enforcement, but the extent, variety and seriousness of the violations recounted in this FBI memo show again that the secret FISA process breeds sloppiness unless there's adequate oversight," Leahy said.