Müller Dairy has been found guilty of wrongly implying its Little Stars range is healthier than Yoplait's Petits Filous.

The Advertising Standards Authority upheld four out of seven complaints against the dairy brand this week.

Yoplait challenged a Müller national press ad showing a grey number 15 with ingredients listed inside it next to a sign that said Petits Filous. A pink number seven in an embroidered style depicted the ingredients in Müller Little Stars, and text below the image stated: "It's simple, Müller Little Stars fromage frais has less than half the ingredients of Petits Filous fromage frais."

The ASA said the ad misleadingly implied Little Stars were healthier than Petits Filous.

The composition and style of the ad could suggest one product was healthier than the other because of the difference in the number of ingredients, it said. It added that the presentation of the two lists of ingredients portrayed Petits Filous in a negative way, with ingredients in each list given differing prominence. Less desirable ingredients such as sugar appeared in smaller text and sideways in Little Stars, but in large text the right way up in Petits Filous, it pointed out.

The ASA also criticised Müller for misleading consumers by emphasising undesirable ingredients in its rival's product when it had similar quantities in its own, and suggested its 'natural' claims were misleading.