WASHINGTON — Four months after the Federal Communications Commission approved a hotly contested merger of Comcast and NBC Universal, one of the commissioners who voted for the deal said on Wednesday that she would soon join Comcast’s Washington lobbying office.

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Meredith Attwell Baker, a former Commerce Department official who worked on telecommunications issues in George W. Bush’s administration, announced that she would leave the F.C.C. when her term expires at the end of June. At Comcast, she will serve as senior vice president for government affairs for NBC Universal, which Comcast acquired in January.

The announcement drew immediate criticism from some groups that had opposed the Comcast-NBC merger. They said the move was indicative of an ethically questionable revolving door between regulatory agencies and the companies they oversee.

The revolving door between government and the lobbyists who seek to influence public policy and legislation on behalf of companies or other organizations was a target of reform by President Obama even before he took office. During the 2008 campaign, he vowed to “close the revolving door” and “clean up both ends of Pennsylvania Avenue” with “the most sweeping ethics reform in history.”

Though Ms. Baker was appointed to what is considered an independent regulatory agency, she signed the administration’s ethics pledge upon taking office in July 2009. Under the pledge, she will not be allowed to lobby anyone at the F.C.C. for two years after her departure.

In addition, Ms. Baker will not be able to lobby other political appointees at the F.C.C., including other commissioners, for the remainder of the Obama administration, including a second term if the president is re-elected. She faces a lifetime ban on lobbying any executive branch agency, including the F.C.C., on the agreement that Comcast made with the commission as a condition of its approval of the merger with NBC Universal.

Ms. Baker can lobby members of Congress immediately upon beginning her new job.

“I am privileged to have had the opportunity to serve the country at a time of critical transformation in the telecommunications industry,” Ms. Baker said in a statement. “The continued deployment of our broadband infrastructures will meaningfully impact the lives of all Americans. I am happy to have played a small part in the success.”

Ms. Baker, one of two Republicans on the five-member commission, recently criticized the speed of the commission’s review of the Comcast-NBC merger, which took 355 days. The F.C.C. voted 4-1 in January for approval, subject to several conditions.

“The NBC/Comcast merger took too long, in my view,” Ms. Baker said on March 2 in a speech to a communications industry group. Noting that that time was similar to the length of other major merger reviews at the commission, she asked whether those reviews were preventing companies from trying to grow through acquisition.

“My concern is that you might walk away,” she told the communications executives, “and how many other consumer-enhancing and job-creating deals are not getting done today.”

Her route of departure was harshly criticized by Craig Aaron, the president and chief executive of Free Press, a media interest group that had opposed the Comcast-NBC merger. Mr. Aaron called the move “just the latest, though perhaps most blatant, example of a so-called public servant cashing in at a company she is supposed to be regulating.”

“No wonder the public is so nauseated by business as usual in Washington, where the complete capture of government by industry barely raises any eyebrows,” Mr. Aaron said. “The continuously revolving door at the F.C.C. continues to erode any prospects for good public policy.”

Ms. Baker issued statements about her departure through both the F.C.C. and Comcast, but she did not address the revolving door issue in those statements. She did not return a phone call to her F.C.C. office seeking comment.

Other interest groups were less vehement in their objections, in part because they viewed Ms. Baker as likely to have voted to approve the Comcast-NBC merger regardless of where her next job would be.

Most of her colleagues on the commission wished Ms. Baker well in official statements.

“She’s made our decisions smarter and our policies better,” Julius Genachowski, the chairman of the F.C.C., said. “I wish her well in her new role at NBC Universal.”

Only one F.C.C. commissioner, Michael J. Copps, who voted against the Comcast-NBC merger, expressed surprise at her departure.