Christine Varney, the top antitrust official in the U.S. Justice Department, is stepping down to become a partner at an elite law firm in New York.

The law firm, Cravath, Swaine & Moore, made the announcement in an internal memo on Wednesday.

Although Varney was appointed by President Obama to beef up antitrust enforcement, she was not considered the hard-nosed enforcer many had expected. She cleared major deals during her two years on the job, including the approval of Comcast Corp's acquisition of a 51 percent stake in NBC Universal from General Electric Co. , creating a $30 billion business that includes broadcast, cable networks, movie studios and theme parks. The deal included the condition that Comcast give up day-to-day control of the video website Hulu.

The Justice Department under Varney also extended controversial approvals of Ticketmaster's buy of Live Nation in 2010 and Google's purchase of ticketing software company ITA in April.

The Justice Department did not immediately respond to request for comment about Varney's departure.

Cravath, a law firm with about 500 attorneys, has a renowned antitrust practice. It represented United Airlines in its merger with Continental, a merger that was completed in October. The firm also has long-represented IBM and Time Warner Cable. The law firm's average profits per partner in 2010 were $3.2 million, according to the American Lawyer. Gross revenue was $591 million.

Prior to becoming Assistant Attorney General for the Antitrust Division, Varney practiced for 10 years at Hogan & Hartson, now Hogan Lovells. She was previously a commissioner at the Federal Trade Commission.

(Reporting by Alison Frankel, Leigh Jones, Erin Geiger Smith and Karey Wutkowski; Editing by Eddie Evans)