Meredith Attwell Baker, one of two Republicans on the five-member Federal Communications Commission, abruptly announced on Wednesday that she is leaving the agency as of June 3.
Earlier, the Wall Street Journal reported that Baker was taking a job in Comcast's Washington lobbying shop.
"After seven years of public service, I sent a letter to President Obama this afternoon thanking him for the distinct honor of serving on the Federal Communications Commission and informing him of my intention to leave the Commission on June 3, 2011," Baker wrote in statement.
The FCC is revving up its review of the proposed $39 billion combination of AT&T and T-Mobile. Baker joined three of her colleagues in January in approving Comcast's joint venture with NBC Universal.
Baker, whose term expires in June, had been widely expected to be renominated for a second term at the commission.