New Delhi: Tobacco products are marketed and sold through unpaid content on Facebook despite the social media company's policies that prohibit or restrict promotion of such items, researchers at Stanford University said in a study released on Thursday.

The study has found unpaid marketing, principally through brand-sponsored Facebook pages, the researchers said, adding that their findings revealed "loopholes" within the social media site's tobacco-related policies that the company could potentially close.

Among 108 company-sponsored pages for leading brands of cigars, e-cigarettes, hookah tobacco and smokeless tobacco, the study found that more than half provided "shop now" buttons that would allow users a way to buy their products, a media release from Stanford University said.

About two-thirds of the pages included sale promotions such as coupons and discounts and all but one featured imagery of a tobacco product, the study has found, the release said.

While Facebook requires restricted access for people under 18 years of age from pages promoting what it calls the "private sale" of regulated goods or services, including tobacco, less than half of these brand-sponsored pages included such an "age gate", the university said in its release. The study was published in The BMJ Tobacco Control, a medical journal, on Thursday.

Response is awaited to a mail sent by The Telegraph to Facebook's media office.

"Our hope is that our study, by highlighting the degree to which tobacco marketers evade Facebook's intended restrictions, will encourage the company to make a renewed effort to implement its well-intentioned policies," Robert Jackler, professor of otorhinolayngology at Stanford University and lead author of the study said in the release.

Jackler and his colleagues looked for company-sponsored Facebook pages among 388 tobacco brands and found such pages for 108, including more than half of 46 hookah tobacco brands and 92 e-cigarette brands.

They also found that 10 of 14 online tobacco stores with company-maintained Facebook pages promoted popular cigarette brands, and included links to purchase them, the university said.

Facebook's advertising policy, which applies to paid ads and commercial content, does not permit images of tobacco. However, 107 of the 108 company-sponsored pages included such imagery, the study found.

The commerce policy, which governs products and services sold on Facebook, prohibits the sale of tobacco and related paraphernalia, the university said in its release.

Facebook last summer banned private individuals from buying, selling or trading tobacco products, but the provision had been removed by February 2018, the researchers said.

The company's advertising policy also bars the promotion of tobacco product sales, but the researchers found purchase links on 58 and sale promotion on 71 of the brand-sponsored pages, the university said.

The university release quotes Jackler as saying the study reveals loopholes in Facebook's tobacco-related policies that the company could potentially close.