The advertising watchdog has banned adverts for two health clinics after they promoted the benefits of the prescription-only medicine Botox.
The Advertising Standards Authority (ASA) said the rulings against Dermaskin Clinics, based in Cardiff, and HB Health of Knightsbridge "set a precedent of what we expect from all advertisers across the sector" and would be followed up by compliance work.
Advertising prescription-only medicines such as Botox to the public is prohibited under UK regulations.
Advertisers who offer the product and other injected treatments can describe them as "cosmetic fillers" or "injected fillers" but cannot name Botox directly.
However both companies named Botox on the home page of their websites, describing it as a "commonly used beauty treatment", while Dermaskin went on to say it was "a proven and safe treatment, which has been in use for over 16 years".
HB Health told the ASA it had removed the reference to Botox from its home page and replaced it with the term "wrinkle softening treatment", but added that references to the product were extremely common within the beauty industry and many clinic websites contained similar content.
Dermaskin agreed to remove the reference to Botox from its home page, but said permitted references to treatments "should take into account normal clinical practice in the UK".
Dermaskin added that the use of Botox for facial lines and wrinkles was "both common and widespread amongst the specialists and doctors within the speciality".
The ASA said Dermaskin's website included claims that went beyond factual references and were a direct promotion of the Botox, such as "this revolutionary treatment ... .is the most popular such treatment in the world" and "thousands of these treatments are performed every year with astonishing results".
It said: "Because many of the direct and implied references to Botox within the website constituted a promotion of a prescription-only medicine to the general public, we therefore concluded that the code had been breached.
The ASA noted that HB Health had changed its website to remove references to Botox, but this had not resolved the issue because visitors who clicked on the replacement text "wrinkle softening treatment" were then connected directly to content about Botox.
It said marketers needed to ensure that references to Botox were only presented in the context of a potential outcome of a consultation with the clinic.
The ASA ruled that both ads should not appear again in their current form and warned both clinics to "take special care when referencing Botox in the future".
The watchdog said: "It is illegal to advertise a prescription-only medicine, such as Botox, to the public. Our rulings, which apply to ads across media including online, set a clear precedent for the whole health and beauty sector.
"Any company referring to Botox must stick to the facts and avoid any promotional language. We'll be communicating this requirement to the sector and providing help and advice so they get their ads right."