An Aldi advert claiming the discounter was “the home of Britain’s cheapest Christmas dinner” misled customers, a watchdog has found.

The four-page wrap-around newspaper ad, published on December 6, also stated: “Sainsbury’s £44.81”, “Aldi £33.80” and “Swap & Save over 20% on your Christmas dinner”, and added: “According to results published by Which?, Aldi’s Christmas dinner came in at over 20% cheaper than Sainsbury’s”.

Small text at the bottom of the ad stated that the comparison related to “seven UK supermarkets”.

Sainsbury’s complained to the Advertising Standards Authority (ASA) that the ad was misleading, and the price comparison was not representative of prices during the period when consumers would be purchasing fresh produce for their Christmas dinner – usually in the last week or so before Christmas Day.

South Wales Argus: The four-page wrap-around newspaper ad from Aldi, published on December 6, was dubbed misleading by the Advertising Standards AuthorityThe four-page wrap-around newspaper ad from Aldi, published on December 6, was dubbed misleading by the Advertising Standards Authority (Image: ASA/PA)Aldi said the claims in the ad were from a comparison by Which? detailed in an article on the consumer group’s website, titled: “Which is the cheapest supermarket for Christmas dinner ingredients”.

Aldi acknowledged that Which? had found that the price difference between Aldi and the second-cheapest supermarket, Lidl, was 4p, and so had also given Lidl a “Budget-friendly Christmas Dinner” award.

The ASA said consumers would understand from the ad that the total cost of buying the ingredients at Aldi for a typical Christmas dinner would be cheaper than in any other British supermarket, so there would be no reason to shop around.

It said consumers would also understand that the price comparison was based on Which? research, and that Which? had given Aldi a “cheapest Christmas dinner” award.

Furthermore, it said the ad’s text that the overall comparison related to seven UK supermarkets, and not all of them, was “so small that many readers would overlook it”.

The ASA also found the ad misled consumers because the comparison related to price checks conducted between November 6 and 27, which were likely to have changed by the time shoppers would be buying their Christmas dinner.

The ASA said: “We told Aldi to ensure that price comparisons with their competitors were not misleading, and that the basis of such comparisons was clear and adequately substantiated.”

An Aldi spokeswoman said: “We are disappointed that the ASA has upheld this complaint based on an advertising technicality, but we remain confident that customers will make significant savings every time they shop with Aldi.

“That’s why we have been recognised by Which? as the UK’s Cheapest Supermarket for three years running.”

A Which? spokesman said: “We support this decision by the ASA: consumers should not be subjected to potentially misleading advertising and it is right that the regulator is holding Aldi to account.

“We are disappointed that a Which? endorsement logo and our research was used in an advert that has broken the regulator’s rules on marketing and we have sought assurances from Aldi that it will not happen again.”