A Food and Drug Administration official with considerable power over authorization decisions for e-cigarettes and products aimed at curbing smoking resigned on Tuesday to work for Philip Morris International, the global tobacco conglomerate and maker of Marlboros.

The official, Matt Holman, was chief of the office of science in the agency’s Center for Tobacco Products. In a memo to the staff on Tuesday, Brian King, the center’s director, wrote that Dr. Holman had announced that he would be leaving — effective immediately — to join Philip Morris. The memo said Dr. Holman had been on leave and, consistent with agency ethics policies, had recused himself from all tobacco center work “while exploring career opportunities outside of government.”

Mr. King lauded Dr. Holman’s 20 years of work at the F.D.A., where he has in recent years been “preparing for and overseeing review” of marketing applications for e-cigarettes and other nicotine-delivery products. Dr. Holman said in an interview on Wednesday that his exact role at Philip Morris had so far been broadly defined but added that he would work on tobacco harm-reduction efforts and provide some input on regulatory submissions to the agency.

His resignation adds further turmoil to the agency’s tobacco control division, which is undergoing a review ordered by Dr. Robert Califf, the agency’s commissioner. The division also lost its longtime director, Mitch Zeller, who retired in April.

To critics, Dr. Holman’s move is a particularly concerning example of the “revolving door” between federal officials and the industries they regulate; in this case, one that has garnered a high degree of public distrust. It has also raised questions about agency approvals, including that of Philip Morris’s IQOS, a “heat-not-burn” tobacco device, which some researchers have found troubling. IQOS is not sold on the U.S. market now because of patent litigation, but if that were resolved, the device could face fresh F.D.A. reviews.

Federal rules governing “revolving door” career moves do not prevent an official from overseeing regulatory matters one week and joining a corporation with products under review the next.

“This is legal. That’s the bottom line,” said Dr. Michael Carome, director of the Public Citizen health research group. “It’s this type of revolving door move that really undermines public confidence in the agency.”

The federal rules do ban Dr. Holman from appearing before the F.D.A. on matters in which he “participated personally and substantially during government service.”

Dr. Holman said that he consulted with agency ethics lawyers before starting job discussions earlier this month. He said he was drawn to Philip Morris because he viewed the company as being committed to the goal of moving cigarette smokers to noncombustible and less harmful products.

“They are taking the actions that I think would align with such a goal,” Dr. Holman said. “And that’s what really drew my attention to P.M.I. I’m going there not to help them sell more cigarettes, but the opposite.”

He brushed off “revolving door” criticisms, saying that if that were his motivation, he could have left the agency for industry many years ago. But lawmakers and some public health experts criticized Dr. Holman’s choice and its effect on the F.D.A.’s decision-making.

“It is embarrassing for the F.D.A., which sees itself as a public health agency, to have its employees go to a company that is a leading manufacturer of death,” said Micah Berman, an associate professor of public health and law at Ohio State University.

Representative Raja Krishnamoorthi, a Democrat of Illinois, was equally critical. “The revolving door between F.D.A. and the industries it is tasked with regulating is extremely disturbing,” he said in a statement. “While some, including P.M.I., may argue that their hire is evidence of P.M.I.’s alleged commitment to taking the health impacts of its products more seriously, I won’t hold my breath.”

As head of the F.D.A. science office, Dr. Holman played a key role in approvals of electronic cigarettes and similar devices, which manufacturers have had to submit for review to stay on the market in recent years.

IQOS, the Philip Morris product that Altria has a license to distribute in the United States, was one of the approved products. It is sold in Korea, Japan and other countries. A company spokesman said U.S. sales were expected to resume next year, but it might have to undergo another review before that.

Critics of the IQOS approval include Stanton Glantz, a retired professor of medicine, and his colleagues at the University of California, San Francisco, who published a study saying the device contained toxins, some potentially carcinogenic and some at higher levels than in combustible cigarettes. The agency’s approval “disregarded valid scientific evidence and misapplied the public health standard mandated by law,” the study in the journal Tobacco Control concluded.

Dr. Glantz said on Wednesday that Dr. Holman ignored another major study showing that e-cigarette use — outside of controlled studies of quitting efforts — was not associated with reduced rates of smoking. He said approvals have done little to deal with the problem of dual-use, or using cigarettes and e-cigarettes, which is worse for overall health. Of Dr. Holman’s departure, Dr. Glantz said, “good riddance.”

“He’s the one who signed off on these approvals,” he said. “They deal with all of these issues by ignoring it, by relying on out-of-date studies.”

Among the F.D.A.’s recent controversies was the decision in June to deny marketing authorization to Juul Labs’ e-cigarettes. Since then, the agency has relented, announcing a review of its decision.

In a court filing, Juul cited the authorization granted to Philip Morris as a reason it would likely prevail, saying IQOS was approved even though a dozen chemicals in IQOS aerosols were “‘potentially genotoxic and/or carcinogenic’ and were ‘present in higher concentration[s]’ than in combustible cigarette smoke.”

Dr. Holman said many agency decisions have their critics, but he believed IQOS authorization was warranted on a full review of the data.

Philip Morris said in a statement that Dr. Holman “is committed to helping existing adult smokers access scientifically substantiated smoke-free alternatives while protecting youth. We are looking forward to him joining our team as we continue to pursue a smoke free future.”

The company also recently hired Keagan Lenihan, a former F.D.A. chief of staff, as a vice president of government affairs.