The complaint to the Advertising Standards Authority was made by rival supermarket chain Tesco and concerned a TV ad, created by Publicis, which said that Asda was "officially the lowest priced supermarket for the seventh year running", with on-screen text stating, "The Grocer Magazine Survey".
Tesco also complained about three national press ads that read: "Asda wins every year... you win every day" and "Yet again, Asda has been voted Britain's Lowest Priced Supermarket -- for the seventh year running".
The ASA upheld concerns made about the meaning of the term "official", because Tesco said it implied The Grocer magazine's annual award for the cheapest retailer in June 2004 was run by a government department or industry body.
The authority said that it considered it too limited a price comparison to substantiate Asda's claim because it used only 33 items and therefore made it vulnerable to "price chasing" by retailers. It also ruled that it implied the consumer would find all products cheaper at all the stores every day.
Tesco argued that 33 products could not represent a "typical" weekly shop and sent the authority its analysis of a 10% sample of the 45m baskets it had sold in a four-week period after the end of the survey cited in the ad.
Asda has argued back, saying that the survey was respected because the magazine has been published since 1862 and that there were examples of where businesses had used "official" to describe the results of other industry awards.
The ASA concluded that because the survey was not taken by a government or industry body whose data was wholly accepted, it advised the supermarket not to repeat the claim.
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