Director S. Elizabeth Birnbaum's decision to leave comes as Interior officials are under fire for failing to ensure the safety of the Deepwater Horizon rig that has been leaking oil into the Gulf of Mexico since it exploded in April.
It also comes on the heels of an inspector general report detailing a cozy relationship between some MMS employees and the oil and gas companies they regulate. The employees accepted hunting and fishing trips, tickets to sporting events and other gifts from the companies, the Interior IG found. Auditors also noted use of illegal drugs and other inappropriate behavior.
Interior Secretary Ken Salazar is reorganizing MMS in hopes of improving management and oversight of drilling. The agency will now have separate enforcement, energy development and revenue collection entities.
"I'm hopeful that the reforms that the secretary and the administration are undertaking will resolve the flaws in the current system that I inherited," Birnbaum said in a statement.
The Associated Press originally reported President Obama asked her to step down, but Salazar said she left on her own volition.
"Elizabeth Birnbaum is a strong and effective person and leader," he said in a statement. "She helped break through tough issues including offshore renewable development and helped us take important steps to fix a broken system."
Birnbaum took over MMS in July 2009, after a stint as staff director for the House Administration Committee. Before that, she spent six years leading advocacy programs for the conservation organization American Rivers. She was not completely new to Interior, having served as associate solicitor for mineral resources from 2000 to 2001, and special assistant to the Interior solicitor from 1999 to 2000.