WASHINGTON (Reuters) - The top U.S. antitrust enforcer, Bill Baer, will be recused from reviewing Comcast Corp's proposed deal to buy Time Warner Cable Inc, the U.S. Justice Department said on Thursday.

The investigation of the $45.2 billion deal will be overseen by two other Justice Department officials: Principal Deputy Assistant Attorney General Renata Hesse and Deputy Assistant Attorney General David Gelfand, a litigator.

In a statement announcing the decision, the Justice Department did not say why Baer, who heads the Justice Department's Antitrust Division, had recused himself.

When Comcast was buying NBC Universal, a deal concluded in early 2011, Baer, then a partner at the law firm of Arnold & Porter, represented NBCU's owner, General Electric.

Hesse has significant experience with big mergers. While at the FCC, she headed the team that reviewed AT&T;'s proposed merger to buy T-Mobile USA. The U.S. government challenged that deal in 2011, and the companies eventually gave up.

The Comcast will also be reviewed by the Federal Communications Commission.

Consumer advocates have criticized the proposed transaction since a combined Comcast and Time Warner Cable would have a near 30 percent share of the U.S. pay television market and would be a major provider of broadband Internet access.

As the U.S. agencies prepare to review the deal, Comcast has been working to burnish its reputation with regulators.

On Tuesday, it announced that its discounted Internet service for low-income families, Internet Essentials, will be available indefinitely. The program has enrolled about 300,000 families since it launched in 2011.

(Reporting by Diane Bartz, editing by Ros Krasny and David Storey)