The consumer rights group, which claimed that the advert, aired in the UK, exaggerated the cereal's healthiness, said that the failure of the Advertising Standards Authority (ASA) to uphold the complaint "highlights the fundamental weaknesses in the way that television adverts for food are currently regulated".
The advert, which shows a sack of rice next to a box of the cereal, tells viewers that there's nothing simpler than the single grain of rice we use to make each Rice Krispie. Kellogg's told the ASA that the ads were designed to communicate that rice was the primary ingredient of the product. They said for every 100 kg of Kellogg's Rice Krispies produced, 99 kg of rice was used.
But Which? complained that the TV ad misled viewers because the cereal contains a lot of salt and sugar, as defined by the Food Standards Agency (FSA).
However the advertising authority argued that once milk was added, the level of salt dropped to 0.41g per 100g, a level considered moderate by the FSA. It said the level of sugar would also drop once milk was added.
"We noted that, without milk, Kellogg's Rice Krispies had 10 g of total sugars per 100 g and understood that the FSA considered that to be a 'medium' level of sugar; when eaten with the recommended serving of milk (125 ml) the level of total sugar was 5.8 g per 100 g which was also considered a "medium" level of sugar by the FSA," said the ASA in its adjudication.
"We noted Kellogg's Rice Krispies offered certain nutritional benefits and were low in fat. We therefore considered that it was not misleading for the ad to imply that Kellogg's Rice Krispies were not an unhealthy breakfast choice."
The ASA also rejected complaints that the advert implied that rice was the sole ingredient in Kelloggs Rice Krispies. It said the advert suggested rice was the primary ingredient and that viewers were unlikely to believe it was the only one.
The Broadcast Advertising Clearance Centre (BACC) said they agreed with the comments made by Kellogg's, and the ASA rejected Which?'s complaint. The authority recommended that no further action be taken.
The ruling has not pleased Which?.
"This highlights the fundamental weaknesses in the way that television adverts for food are currently regulated and the need for much tighter controls," said chief policy adviser Sue Davies.
"Which? remains convinced that this advert was misleading and is disappointed that the ASA has failed to consider this from the consumer's rather than the company's perspective."
The ruling over the Rice Krispies advert was taken in the context of the ongoing debate over the role that TV advertising to kids plays in informing healthy eating habits. While the food industry believes that self-regulation is the best way forward, some organisations are demanding regulations to curb harmful marketing practices.
In July, Which? published a report highlighting the need for manufacturers to reduce the sugar, salt and fat in many of their cereals targeted at children, and called for more responsible marketing and labelling. And more recently, a University of Sussex report recommended restricting the marketing and advertising of certain categories of food and drink, especially to children and young people.
"Advertising has a proven effect on children's food choices," said Davies. "Irresponsible advertising on TV is an uninvited guest in our homes, contributing to the growing national obesity crisis."