WASHINGTON (CNN) -- The FBI continued in 2006 to badly mishandle letters that it uses to obtain personal records without a court order, according to a Justice Department report released Thursday.
FBI Director Robert Mueller testifes about oversight before a Senate committee last week.
The new report cites "issuance of NSLs [national security letters] without proper authorization, improper requests and unauthorized collection of telephone or Internet e-mail records due to FBI errors or mistakes made by NSL recipients."
But a top department official said significant progress has been made in the past year toward correcting those errors.
Inspector General Glenn Fine said it's too soon to tell if the problems will be eliminated.
Thursday's report came a year after Fine's first report on national security letters, which the FBI issues to third parties to get information on individuals -- such as telephone, e-mail and financial records -- in connection with terrorism or spy investigations.
The original report, which covered 2004 and 2005, found serious systematic failures by the bureau in its use of the letters.
Fine said it is no surprise that the latest report found continued violations in 2006, since that was before he issued last year's stinging appraisal.
"The FBI and DOJ [Department of Justice] have made significant progress in implementing the recommendations contained in our first report and in adopting additional corrective measures to address the serious problems," Fine said.
"However, several of the FBI's and the department's corrective measures are not yet fully implemented and it is too early to determine whether these measures will eliminate the problems with the use of these authorities," he said.
The Justice Department and FBI were quick to latch onto Fine's comments and praise the FBI for doing a much better job, but Democratic lawmakers were just as fast to pounce on the report as evidence of continued FBI failings.
"We are pleased with the Office of Inspector General's positive assessment of the many actions taken by the Justice Department and FBI to improve oversight of the use of national security letters," said spokesman Dean Boyd of the Justice Department's National Security Division.
"Despite the low error rate, we continue to strive for zero errors and we believe that the measures we have put in place will help ensure that," an FBI statement said.
But Senate Judiciary Committee Chairman Patrick Leahy, a Vermont Democrat, promised to hold a hearing on the issue. The report, he said, "outlines more abuses and what appears to be the improper use of national security letters for years in a systemic failure throughout the FBI."
House Judiciary Committee Chairman John Conyers, D-Michigan, said, "At the same time the administration is trying to intimidate the Congress into giving it additional spying power, we find out yet again that it has abused its authority to pry into the lives of law-abiding Americans."
The committee's ranking member -- Rep. Lamar Smith, R-Texas -- praised the FBI and Justice Department improvements.
Smith cited the FBI's establishment of an Office of Integrity and Compliance to monitor procedures, and a new Oversight Section opened in the Justice Department's Office of Intelligence.
"These are precisely the kinds of steps Congress urged the FBI to take last year," Smith said.
The new report shows the FBI continued in 2006 to increase its use of the secret letters. The 49,425 requests represented a 4.7 percent increase over 2005.
In 2006, FBI agents using NSL requests sought secret data on more than 11,500 U.S. citizens and resident aliens, compared to 6,500 in 2003, the report said.
There were also about 8,600 requests for information about "non-U.S. persons " -- which includes visiting and illegal foreigners -- compared to 10,200 in 2003.
In an accompanying report, the inspector general said the FBI made 47 requests to the Foreign Intelligence Surveillance Court for warrants to pursue business records. All requests were approved.
The report, however, highlighted one classified case in which the secret FISA court turned down a draft application because "the facts were too thin and this request implicated the target's First Amendment rights."
Frustrated FBI General Counsel Valerie Caproni then authorized the FBI to pursue the matter anyway through the use of national security letters, which provided access to telephone and e-mail records without a court order.
The inspector general said that during his investigation he asked the FBI's top lawyer whether she had reviewed that case in light of the FISA court's concerns, and she said she had not. E-mail to a friend