Asda has been slapped on the wrist by the advertising watchdog for fudging a price comparison with Argos.

The supermarket ran a TV ad last October claiming it had 551 branded products cheaper than Argos, while Argos had 139 cheaper than it.

Argos complained to the Advertising Standards Authority, saying both retailers offered far more identical branded products than the ones featured in the ad, and that more than 139 of those products were cheaper in Argos.

Argos also argued that prices fluctuated so quickly in the current retail environment that any comparison could only be valid for 24 hours.

The ASA disagreed with the second complaint, saying the ad made clear the date on which the price comparison had been made, and that it was only broadcast for a few days.

But it agreed that Asda had not made it clear there were significant limitations and qualifications to the basis of the price comparison. It said the supermarket had flouted advertising rules on misleading advertising, substantiation, qualification, exaggeration, comparisons with identifiable competitors and price comparisons.

The ASA banned the ad and warned Asda to ensure that all future price comparisons could be substantiated and were not misleading.