The ASA ran the rule on the fashion house's new 'The Cruise 2016' campaign, which first appeared in Britain in December 2015.
It judged that the female model in question, Avery Blanchard, who is seen in one still from the video leaning against a wall in a long-sleeve printed dress - with, it must be said, a noticeably thin torso - was too thin in the way it was presented, reported New York Times.
Gucci also pointed out that "nowhere in the ads were any models' 'bones' visible, their make-up was natural rather than heavy" and that the lighting was "warm to ensure there were no hollows caused by shadows and their clothes were not revealing."
However, this didn't sway the ASA, which ruled: "We considered (the model's) torso and arms were quite slender and appeared to be out of proportion with her head and lower body. We also considered that her sombre facial expression and dark make up, particularly around her eyes, made her face look gaunt.
Campaigners have long argued that overly skinny models can damage the confidence of young women and girls by promoting unrealistic and unhealthy body images.