The federal watchdog whose report on lavish conference spending by the General Services Administration prompted government-wide reforms has resigned his position.

GSA Inspector General Brian D. Miller said in a letter to President Obama on Monday that his last day with the government will be April 18. He plans to move to the private sector, where he will work with Navigant, a dispute- and investigation-advisory firm, according to a GSA announcement.

GSA Inspector General Brian Miller answers questions from the House Committee on Oversight and Government Reform as it investigates wasteful spending and excesses by GSA officials. (J. Scott Applewhite/AP)

“I count myself fortunate indeed to have worked on so many important and interesting cases, audits and investigations in my federal career,” Miller said in the announcement. He added: “My federal career has been unbelievably exciting and I am sorry to leave federal service.”

Miller served as a federal prosecutor with the Justice Department for more than a decade before President George W. Bush nominated him to become the GSA’s inspector general in November 2004. The Senate confirmed him by unanimous vote in July 2005.

During Miller’s tenure as inspector general, his office made a series high-profile discoveries. Its reports revealed that a former GSA chief of staff had covered up efforts to assist Jack Abramoff in acquiring GSA-controlled properties, exposed a network of federal officials who accepted bribes, and showed that GSA managers had improperly intervened in contract negotiations.

Miller’s office also worked on a project to recover lost and stolen New Deal-era artwork produced under federal programs such as the Works Progress Administration. In 2011, he made an appearance on PBS’s “Antiques Roadshow” to discuss his work in that area.

“Brian and his team have been essential in ensuring that this agency is delivering on its mission with the efficiency and transparency that the American people expect and deserve,” GSA Administrator Dan Tangherlini said in a statement on Monday. “We are grateful for the strong legacy he leaves behind, and I know that I speak for all my colleagues when I say that we wish him well in all his future endeavors.”

As a federal prosecutor, Miller’s work included helping with the prosecution of accused terrorists such as Zacarias Moussaoui. He also worked on a fraud case involving science grants, for which he received an award from the Executive Office for U.S. Attorneys.

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