Three ads for Aldi claiming customers could make significant savings compared with the "big four" supermarkets have been banned for being unfair and not "truly representative".
The two television ads claimed a £70 Aldi shop would cost £98 at the big four grocers and compared a £33.04 Aldi basket with the equivalent at its competitors, which it claimed would cost £53.35.
A press ad read: "When it comes to the crunch, Aldi win every time. Other supermarkets go up, down, all over the place. But Aldi have 'everyday low prices', so you know where you stand."
Morrisons and two members of the public said the ads did not make it sufficiently clear that they compared prices of Aldi's own-brand products with branded products sold at Morrisons and other supermarkets, which all sold their own cheaper own-label equivalents.
Aldi said consumers were likely to interpret the comparison as intended - the branded and fresh products from Tesco, Asda, Sainsbury's and Morrisons shown versus the Aldi products shown.
It believed consumers would know that its competitors stocked own-brand products which met the same need and would likely be cheaper and, in any case, on-screen text read: "Other supermarkets may sell 'own brand' products at different prices."
The Advertising Standards Authority (ASA) said consumers would understand from the ads that by swapping from shopping at their usual big supermarket to shopping at Aldi they could make significant savings.
The ASA said it was unlikely that price-conscious shoppers would buy such a large proportion of branded items when own-brand goods were typically available.
It said: "We acknowledged that Aldi stated they had not intended the comparisons to represent a 'typical' weekly shop, but to be a comparison between the pictured products only.
"Nonetheless, we considered that was how consumers would interpret the ads rather than as a representation of the savings which could be made by switching from a largely branded shop to shopping in Aldi, and therefore assessed them on that basis."
It added: "Because the ads implied that by swapping from their usual big supermarket to shopping at Aldi, consumers could make savings of the levels highlighted in the ads, rather than presenting the comparison as a representation of the savings which could be made by switching from a largely branded shop to shopping in Aldi, and we had not seen evidence to demonstrate that was the case we concluded that the ads were misleading."
Aldi's UK and Ireland chief executive Matthew Barnes said: "We are extremely disappointed with the ASA's decision, which is ambiguous and inconsistent.
"The use of comparative advertising is a well-established principle and is firmly in the interests of consumers and encourages competition between retailers.
"We will work within this new guidance from the ASA and continue to promote the significant price gap between Aldi's quality, award winning products and their higher priced brand equivalents."