When it comes to e-cigarettes, public health experts and regulators are struggling with deep contradictions and questions, the most fundamental of which is whether e-cigarettes will lure thousands of cigarette smokers away from a deadly habit or actually lead to a new generation of nicotine addicts.

In a report issued last month, the World Health Organization urged stronger restrictions on e-cigarettes, including indoor smoking bans, and also expressed “grave concern” at the growing role of tobacco companies in the industry.

Smaller e-cigarette companies are skeptical too. “To the uninitiated, it looks like they are responsible corporate citizens,” said Cynthia Cabrera, executive director of the Smoke-Free Alternatives Trade Association, an e-cigarette industry group. She considers the warnings “disingenuous,” particularly the MarkTen claim that nicotine is “very toxic” when inhaled, swallowed or brought into contact with the skin. That is not true of the doses in e-cigarettes, she said.

Ms. Cabrera said she believed that the big tobacco companies had an ulterior motive, perhaps to appear to regulators and lawmakers as more credible than the small e-cigarette companies. She speculated that big tobacco companies would then be able to lobby for rules and laws that would favor them. She said some lobbyists were telling legislators that prepackaged, uniform e-cigarettes had lesser health risks than the ones sold, sometimes in made-to-order fashion, in independent vapor shops. In terms of warnings, Ms. Cabrera’s group has called for childproof packaging on e-liquids, which are used to fill e-cigarettes, and they favor warnings calling nicotine addictive and listing other ingredients.

For now, there are hundreds of smaller e-cigarette companies, many selling online, and their claims and warnings run the gamut. Some make health claims that Dr. Jackler said were wild and unsubstantiated, claiming to be sex stimulants, beneficial for insomniacs or even a way to promote weight loss. Dr. Jackler speculated that one motivation for Big Tobacco could be discouraging smokers from using a competing product.

Mr. Phelps, from Altria, dismissed that idea. “We want that category to be successful, and NuMark has taken a number of steps to be a leader,” he said.

The warnings on the MarkTen are far more elaborate than those on a pack of Marlboros, which note, for instance, that “smoking by pregnant women may result in fetal injury, premature birth and low birth weight.” The warning does not include other risks, like the addictive nature of cigarettes, which are known to cause cancer and other deadly diseases. Mr. Phelps said that Altria was putting out cigarette warnings mandated by the government. The government mandate does not, however, preclude stronger warnings from appearing on Marlboros.