A senior Republican lawmaker is looking into allegations that a former general counsel of the FBI bore greater responsibility for abuses of surveillance authorities than previously known.

The former official, Valerie E. Caproni, left the FBI in 2011 and has been nominated by President Obama to be a judge in the Southern District of New York.

As general counsel, Caproni and her office had legal oversight over the bureau’s use of intelligence-gathering tools called national security letters, or NSLs, and exigent letters, both of which were used to obtain phone and e-mail records of U.S. citizens and residents without a court sign-off.

In a series of often critical reports from 2007 to 2010, the Justice Department’s Office of the Inspector General pointed out lapses in the bureau’s use of these tools. The reports show that FBI agents over a three-year period ending in 2005 served more than 140,000 national security letters on companies without retaining evidence that the data collection was legal, without ensuring that the data were relevant to government needs and without correctly reporting efforts to Congress.

The bureau’s use of exigent letters — which are supposed to be used only in emergencies and followed up by documentation of an underlying investigation — also sidestepped rules in 2002 and 2006, according to the inspector general.

In a Jan. 17 letter to the current inspector general, Sen. Charles E. Grassley (Iowa), the ranking Republican on the Senate Judiciary Committee, said he had “received an allegation that Ms. Caproni’s actions regarding the NSL program were criticized in initial versions of the reports that were subsequently modified in the final publication.”

A spokesman for Caproni, who is now general counsel at Northrop Grumman, declined to comment. The IG also declined to comment.

The reports state that Caproni’s office held the only central database tracking the use of NSLs. But they do not assign her any particular culpability for the abuses. One report stated that she learned about the use of exigent letters in 2006 after the IG had begun its investigation.

At a congressional hearing in 2007, then-Inspector General Glenn A. Fine said the lapses were the result of “mistakes, carelessness, confusion, sloppiness, lack of training, lack of adequate guidance and lack of adequate oversight.”

Rep. James F. Sensenbrenner (R-Wis.), a Judiciary Committee member, grilled Caproni on why so many NSLs were being issued. “Do we have that many potential terrorists running around the country?” he asked. “If so, I’m really worried.” He accused the FBI of “gross overreach.”

At the hearing, Caproni attributed the missteps to poor controls, and apologized. “We’re concerned,” she said. “And we’re going to fix it.”

The bureau ended the use of exigent letters for phone records in late 2006.

Grassley has asked to receive copies of the draft reports, working papers and other documentation by Feb. 11.