The maker of Colgate toothpaste has been warned not to repeat its famous advertising claim that "more than 80% of dentists recommend Colgate".
Colgate's claim on posters was "misleading"
The Advertising Standards Authority concluded the claim on Colgate posters was "misleading" after investigating the phone survey behind the boast.
It found the dentists surveyed were allowed to name more than one brand.
But the ASA said the advertising claim implied 80% of dentists recommended Colgate to the exclusion of its rivals.
In fact, the ASA's inquiry found another competitor's brand was recommended almost as much as Colgate was by those dentists who were surveyed.
It added the survey "did not make clear the poll was on behalf of Colgate".
The watchdog also said the claim implied professional endorsement of the product by dentists, but Colgate did not have written permission from the interviewees.
In response, toothpaste maker Colgate-Palmolive said it had commissioned a research agency to survey dentists and hygienists on a wide range of subjects each year.
It said the participants would be aware that the survey results might be used for a variety of reasons, including advertising.
But the ASA ruled that the poster advert for Colgate's Total Advanced Fresh toothpaste had breached the industry code's clauses relating to substantiation, truthfulness, testimonials and endorsement of medicines, and upheld the two complaints it had received.