Tesco has won its latest spat at the UK's Advertising Standards Authority (ASA) with rival retailer Asda.

Tesco, the UK's largest grocer, has challenged a national press ad headed "The big Asda Rollback", taking issue with the claim: "Lower prices on everything you buy, week in week out". The company said the claim was misleading as it was unclear as to whether it compared Asda's prices in a previous week or those of their competitors.

Additionally, Tesco said that its own price checks made in January showed that Asda had not made the reductions in each category as claimed in the ad. Tesco argued whether the claim "Lower prices than any other supermarket" was misleading because Asda's prices had been compared with only one segment of the supermarket sector.

In its defence, Asda said it believed the ad "clearly set out" that it was promoting its own price reductions, believing the average consumer was aware that Rollback referred to price reductions against its previous prices.

It also said the phrase "Lower prices on everything you buy, week in, week out" referred to Asda's position only, that there was no reference to their competition and that the ad listed the number of prices Asda had lowered in each category.

Additionally, Asda said its claim: "Lower prices than any other supermarket" was linked by a "+" symbol which stated "Comparison made against Tesco, Sainsbury's and Morrisons only" which it believed clarified, rather than contradicted the claim.

The ASA, however, upheld Tesco's claim. It said: "We concluded that the 'Lower prices than any other supermarket' claim in Asda's ad was misleading."

The ASA has told Asda to make it clear when price comparisons are made with its own prices, to ensure that future ads did not imply a large number of reductions had been made in the preceding week if that was not the case.

The watchdog also asked Asda to ensure that future ads did not suggest price comparison claims related to all other supermarkets when they in fact related to same brand and size products at specific supermarkets only.

The ASA recently banned a Tesco basket comparison ad following complaints from Adsa.