Secretary Lawrence Small, whose tenure at the Smithsonian Institution has generated controversy, tendered his resignation from the post today, effective immediately.

In an internal memo circulated through the Smithsonian staff obtained by The Hill, Roger Sant, chairman of the Smithsonian Board of Regents, alerted employees that he and Regent Patti Stonsifer would hold a 12:30pm news conference to announce Small’s resignation.

“Although the past few weeks have been difficult for us all, we believe that the important work of the Institution will continue and we hope you share our optimism for the future,” Sant wrote.

Small's letter of resignation was accepted by John Roberts, chief justice of the Supreme Court and chancellor of the Smithsonian, according to a statement released today by the Smithsonian.

“The Board of Regents accepts your decision with sincere appreciation for your lasting contributions over the past seven years. The Board recognizes that the Smithsonian Institution has benefited greatly from your leadership and dedication,” Roberts said in a letter to Small. “I speak on behalf of the full Board in observing that the future of the Smithsonian remains bright.”

Recent disclosures of Small’s expense reports showed numerous questionable expenses that he billed to the Smithsonian including $3,464.50 for first-class plane tickets for himself and his wife, as well as $2,800 for a chauffeured car service for a four-day trip. Small also allegedly pressured former Smithsonian Inspector General Debra S. Ritt to avoid including his business expenditures in her recent audit.

Sen. Chuck Grassley (R-Iowa), who has criticized Small’s expenditures, welcomed Small’s resignation. In a statement released shortly after the announcement, he called on the Smithsonian’s board of regents to increase oversight and accountability at the Smithsonian.

“It’s a positive step to have a leadership change,” Grassley said, “The secretary is only part of the Smithsonian’s leadership. The other part is the board of regents. The board needs to continue to recognize its responsibility and take action. I look forward to working with the board on governance reforms and also to ensure that the new secretary will restore the institution’s status as a point of national pride.”

Cristian Samper, director of the Smithsonian's National Museum of Natural History, will be Acting Secretary while the Board of Regents conducts a nationwide search for Small's replacement.