The Advertising Standards Agency has ruled that Asda commercials claiming the supermarket’s prices were lower than those of key rival Tesco lacked evidence and were misleading to consumers.

The ASA yesterday announced that it had upheld a complaint brought by Tesco about the adverts, which cited independent data suggesting Asda offered 2,916 products cheaper than its rival, compared to 962 products that were cheaper at Tesco.

However, the body said Asda had since been unable to substantiate the price claims and backed suggestions by Tesco that the Asda prices used in the comparison were artificially low.

Around 100 products cited as being cheaper at Asda had in fact been cheaper at Tesco when the adverts were produced, the ASA said, while a further 50 products said to be cheaper at Asda were priced equally.

The ruling, which ensures the adverts will not be repeated in their current form, comes with Asda and Tesco set to engage in a new price war following major moves by both groups this week to woo consumers feeling the pain of the economic downturn.