William Blumenthal, who served almost four years as general counsel for the Federal Trade Commission, plans to leave the agency to return to private law practice.

Blumenthal, who joined the Commission in February 2005, will join Clifford Chance as a partner in the firm’s mergers and acquisitions practice and chairman of its U.S. antitrust group.

As general counsel at the FTC, Blumenthal oversaw the agency’s role in developing and presenting the federal government’s position in several matters before the U.S. Supreme Court, and oversaw more than two dozen appellate cases. Blumenthal also acted for the Commission in formulating the agency’s position in several intellectual property cases.

In addition, he played a significant role in influencing international competition policy with officials in China, India, Japan, and Korea, as well as competition and consumer protection matters with the European Commission.