The complaint against the video ad on the Colgate website, dating back to August 2014, was brought by Procter & Gamble UK, which owns rival brand Oral-B.
P&G argued that three claims contained in the video's voiceover were misleading: the phrases "revolutionary new toothpaste", "instantly whiter" smile/look, and "much whiter". It also objected to the text "temporary visual effect provided by clinically proven optic brighteners", which was shown on screen at the end.
The ASA dismissed the first, second and fourth of these, thanks to a large amount of evidence provided by Colgate-Palmolive to support the claims.
It found that the first claim was valid because the toothpaste contained a technology called optic brighteners, which had not been used before in another toothpaste in the UK.
It also said the second and fourth claims were acceptable, because the optic brighteners apply a blue pigment to the teeth that gives them an immediate whiter appearance.
But on the third claim, the ASA said consumers would understand this to refer to the immediate whitening effect. Although there was evidence that this effect was noticeable, the watchdog said the phrase "much whiter" exaggerated the effect, which was small.
The ad must not be used again in the form complained about.