U.S. SEC Commissioner Luis Aguilar plans to leave the agency in December, he said in a statement on Monday.
Aguilar, a Democrat whose career began as a staff attorney at the Securities Exchange Commission more than 30 years ago, notified President Barack Obama of his upcoming departure in a letter, he said.
Obama selected Democrat Lisa Fairfax on Oct. 20 to replace Aguilar, whose term has expired. The appointment of Fairfax, a law professor at George Washington University, must be confirmed by the Senate before she can start serving her term.
A hearing date has not been set.
Aguilar will leave at the end of December, or earlier, if Fairfax is confirmed, he wrote in a letter to Obama.
Aguilar, initially nominated to the SEC by former President George W. Bush, is one of three commissioners in the agency's history to have been nominated by two different presidents from two different political parties, he wrote.
Aguilar started the position in July 2008, about two months before Lehman Brothers Holdings Inc filed for bankruptcy. Lehman, once the fourth-largest U.S. investment bank, held large quantities of risky subprime mortgage securities.
The bank's collapse helped to trigger the global financial crisis, which led to the Dodd-Frank financial reform law and numerous new SEC rules.
"There is undoubtedly more work to be done, but much progress has been made to protect investors and strengthen our capital markets," Aguilar wrote in his letter.
Obama nominated Aguilar for a second term in 2011.
In October, Obama also nominated Republican Hester Peirce to serve as an SEC commissioner. Peirce, a senior research fellow and director of the financial markets working group at the Mercatus Center at George Mason University, would replace Daniel Gallagher, who stepped down in early October.
Peirce's nomination is also subject to Senate approval.
(Reporting by Suzanne Barlyn; Editing by Meredith Mazzilli and Dan Grebler)