Four vaping companies, including British American Tobacco (BAT), have been banned from promoting their products on public Instagram pages.
Health activists described the decision as "a big step forward."
UK regulations prohibit online advertising for electronic cigarettes, however, BAT, Ama Vape Lab, Attitude Vapes and Mylo Vapes argued that their Instagram posts simply provided permissible factual information such as name, content and price of your products.
The decision comes as new research suggests that e-cigarette vapor increases the potential of lung bacteria to cause damage and increase inflammation.
There are major concerns around vaping security.
The Advertising Standards Authority (ASA) disagreed with the e-cigarette companies' argument that the posts "clearly outnumbered the provision of factual information" and were promotional in nature.
The ruling followed complaints from Action on Smoking and Health, Stopping Organizations and Products (Campaign for Tobacco Free Kids and Stop), that the posts violated advertising rules by promoting unlicensed e-cigarettes containing nicotine and its components on Instagram.
Seven BAT Instagram posts for their brand of Vype e-cigarettes were reviewed, three of which featured subtitled photos of singer Lily Allen.
The ASA said a social media page or account could be within the rules if found only by those actively seeking it.
But he noted that it was possible for posts from a public Instagram account to be automatically distributed to users following the hashtags they contained, or that the posts could be displayed on another user's Instagram Exploration page.
ASA said: "We considered that both mechanisms were consistent with content sent to consumers without having chosen to receive the message they contained, and therefore that no mechanism was equivalent to actively seeking information about e-cigarettes."
He added that these posts from an Instagram public account "were not analogous to a retailer's website" and therefore were "subject to a ban on advertising unlicensed and nicotine-containing electronic cigarettes, meaning that promotional content is not allowed. or factual. "
The Advertising Standards Authority (ASA) determined that the posts went beyond providing factual information.
ASA also found that the ads contained content that "clearly exceeded the provision of factual information and was promotional in nature."
Simon Cleverly, BAT's head of corporate affairs, said: "In relation to the complaint that we were promoting unlicensed nicotine-containing e-cigarettes and their components on Instagram, while we believed that the content included in the complaint complied with the CAP code of ASA, we will comply with ASA's decision and recommendation to remove the relevant posts and change Instagram account settings. "
Professor Anna Gilmore, director of the University of Bath's Tobacco Control Research Group, Stop's research partner, said: "This is a big step forward to prevent the tobacco industry from promoting its new addictive products for children and adolescents. .
ASA noted that posts could be distributed to users by following the hashtags they contained.
Deborah Arnott, executive director of the Action on Smoking and Health charity, added: "BAT's defense that all they were doing was providing 'social media' information without promoting their products was exploded.
"ASA's decision leaves no doubt that BAT's social media tactics for Vype were irresponsible and illegal and should never be repeated."
Meanwhile, researchers at Queen's University in Belfast found that the bacteria often found in the lungs became more harmful and caused increased inflammation when exposed to electronic cigarette vape.
Vaping has been suggested as a safer alternative to smoking.
The study, published in Respiratory Research, showed that increased lung inflammation is due to bacteria made more virulent by exposure to electronic cigarette vapor.
Deirdre Gilpin, lead author of the study, said: "Bacteria have long been associated with the development of lung diseases such as bronchitis and pneumonia, where smoking plays a role. Our study is the first of its kind aimed at comparing the effect of smoke from cigarette and electronic cigarette vapor in the main pulmonary bacteria ".
Vaping has been suggested as a safer alternative to smoking, although there is limited evidence to support this and there are major concerns around its safety.