WASHINGTON - Senior officials of the Federal Bureau of Investigation repeatedly approved the use of "blanket" records demands to justify the improper collection of thousands of phone records, according to officials briefed on the practice.

The bureau appears to have used the blanket records demands at least 11 times in 2006 alone as a quick way to clean up mistakes made over several years after the Sept. 11, 2001, attacks, according to a letter provided to Congress by a lawyer for an F.B.I. agent who witnessed the missteps.

The F.B.I. has come under fire for its use of so-called national security letters to inappropriately gather records on Americans in terrorism investigations, but details have not previously been disclosed about its use of "blanket" warrants, a one-step operation used to justify the collection of hundreds of phone and e-mail records at a time.

Under the USA Patriot Act, the F.B.I. received broadened authority to issue the national security letters on its own authority - without the approval of a judge - to gather records like phone bills or e-mail transactions that might be considered relevant to a particular terrorism investigation. The Justice Department inspector general found in March 2007 that the F.B.I. had routinely violated the standards for using the letters and that officials often cited "exigent" or emergency situations that did not really exist in issuing them to phone providers and other private companies.

In an updated report due out on Thursday, the inspector general is expected to report that the violations continued through 2006, when the F.B.I. instituted new internal procedures.

The inspector general's ongoing investigation is also said to be focusing on the F.B.I.'s use of the blanket letters as a way of justifying the collection of large amounts of records at one time. F.B.I. officials acknowledged the problem Wednesday, calling it inadvertent, and said officials had been instructed that they could no longer issue blanket orders. Instead, officials have to determine why particular records are considered relevant.

A letter sent last week to Senator Charles E. Grassley, Republican of Iowa, provides new details on the F.B.I.'s use of the national security letters, including the practice of issuing the blanket demands.

A copy of the letter was provided to The Times. It was written by Stephen M. Kohn, a Washington lawyer representing Bassem Youssef, an F.B.I. agent who reported what he thought were abuses in the use of national security letters and was interviewed for three days by the inspector general. In a separate matter, Mr. Youssef is suing the F.B.I. in a discrimination claim.

Mr. Grassley said Wednesday that he was concerned by the issues raised in Mr. Kohn's letter.

"In the past, the F.B.I. has shown a propensity to act as if it were above the law," he said. "That attitude clearly needs to stop. Part of the way we can help the F.B.I. clean up its act is to pay close attention to information from whistle-blowers like Bassem Youssef. We need aggressive follow-up from the inspector general to ensure accountability and reform."

By 2006, F.B.I. officials began learning that the bureau had issued thousands of "exigent" or emergency records demands to phone providers in situations where no life-threatening emergency existed, according to the account of Mr. Youssef, who worked with the phone companies in collecting records in terrorism investigations. In these situations, the F.B.I. had promised the private companies that the emergency records demands would be followed up with formal subpoenas or properly processed letters, but often, the follow-up material never came.

This created a backlog of records that the F.B.I. had obtained without going through proper procedures. In response, the letter said, the F.B.I. devised a plan: rather than issuing national security letters retroactively for each individual investigation, it would issue the blanket letters to cover all the records obtained from a particular phone company.

"When Mr. Youssef was first informed of this concept, he was very uncomfortable with it," his lawyer, Mr. Kohn, said in his letter to Senator Grassley. But the plan was ultimately approved in 2006 by three senior officials at highest levels of the F.B.I., and in the process, Mr. Kohn maintains, the solution may have worsened the problem.

"They made a mistake in cleaning up a mistake," Mr. Kohn said, "because they didn't know the law."

An F.B.I. official who asked for anonymity because the inspector general is still examining the blanket warrant issue said the practice was "an attempt to fix a problem."

"This was ham-handed but pure of heart," the official said. "This was nothing evil, but it was not the right way to do it."

© 2008 The New York Times