The Food and Drug Administration struck the wrong balance in its oversight of the e-cigarette industry, former Food and Drug Administration chief Scott Gottlieb said at CNBC's Healthy Returns conference Tuesday.

While commissioner, Gottlieb championed e-cigarettes as a way to help adults stop smoking. The agency's delayed oversight has been blamed, in part, on a rise in teen vaping that Gottlieb eventually labeled an "epidemic."

One of his worst days as commissioner came last summer when he received data from the annual National Youth Tobacco Survey showing a spike in teens using e-cigarettes, he told CNBC's Meg Tirrell at the conference.

The FDA called the top five manufacturers late last year to submit plans to fix this and proposed limiting sales of fruity flavors to age-restricted stores like vape shops. It also moved up the deadline for manufacturers to apply to have their products reviewed by the FDA by one year, which Gottlieb pushed back when he started as commissioner in 2017.