An Asda "rollback" promotion, launched in the summer, wrongly implied that price cuts on more than 2,400 lines were permanent, the authority said.
A press advertisement said: "At Asda we believe in Permanently Low Prices that stay low, not short-term promotions." However, shoppers noticed that some products reverted to higher prices after a short time.
The ASA upheld the complaints, noting that "not all prices in the promotion stayed reduced". It concluded that "claims such as `We're permanently reducing prices'... misleadingly implied that all lines in the promotion stayed at permanently reduced prices".
Asda said the term "permanent" referred to its long-term pricing strategy, and that 90 per cent of products in its "rollback" stayed at the reduced prices.
The ASA said that Sainsbury's claim to be the first major supermarket chain to ban GM ingredients from its own-label products was misleading as Waitrose and Iceland, which it considered major chains, had done so earlier.Reuse content