Melanie Sloan, the executive director of the liberal-leaning Citizens for Responsibility and Ethics in Washington, formally announced Friday morning that she is leaving her post to practice law with Lanny Davis, a Clinton administration lawyer.

“Since I founded this organization in 2003, CREW has become a powerful force in Washington, holding corrupt politicians’ feet to the fire no matter their political persuasion, relentlessly fighting for campaign finance reform, and pursuing common sense policy changes in an effort to build a better Washington,” Sloan wrote in an e-mail Friday morning. “2011 will bring a new Congress and new challenges for CREW. Twenty of the Most Corrupt Members of Congress will be returning to Washington, and it will be up to all of us to keep them honest.”

Sloan’s successor has not been named, but she is expected to leave the organization in late January and will join Davis’ firm “in several months,” she wrote.

The former White House counsel left McDermott Will & Emery last spring to start his own legal, lobbying and communications shop, Lanny J. Davis & Associates. Since then, Davis has signed up Equatorial Guinea, Martek Biosciences Corp. and the Coalition for Educational Success, according to Justice Department and Senate lobbying records.