Marks & Spencer is taking Aldi to court in a bid to protect its Colin the Caterpillar cake.
The retailer has accused the discounter chain of riding on its reputational coat-tails after Aldi began selling its own Cuthbert the Caterpillar cake, which looks very similar.
M&S claims it infringes its trademark and could lead shoppers to falsely believe the two products are sourced to the same standards.
Lawyers at Dentons logged an intellectual property claim with the High Court this week asking Aldi to stop selling the Cuthbert cake and agree not to sell anything similar in the future.
Aldi said it had not stocked the cake since mid-February and declined to comment further.
Colin the Caterpillar first went on sale about 30 years ago. The sponge cake is filled with milk chocolate and buttercream, and topped with chocolate, sweets and a smiling white chocolate face. The 625g cake costs £7 - £1.12 per 100g.
Cuthbert is £4.99 or 80p per 100g and also has a log-shaped chocolate sponge cake with a chocolate shell.
Colin's appearance has remained largely unchanged for more than 15 years, according to the company, although M&S regularly launched sister products such as Connie the Caterpillar and Halloween and Christmas versions.
Other supermarkets have created their own similar cakes after M&S designed theirs including Waitrose's Cecil, Sainsbury's Wiggles, Tesco's Curly, and Asda's Clyde the Caterpillar.
John Coldham, IP partner at law firm Gowling WLG, said that the two products were "very similar indeed - much closer, it seems, than other caterpillar cakes offered by other retailers".
He said this could be why M&S had taken legal action against Aldi: "Trademark cases on shapes of products are notoriously difficult, as most recently seen by Nestle in its attempts to protect the shape of a KitKat, but all these cases turn on the evidence. M&S will presumably be confident that it has sufficient evidence of the shape's distinctiveness to prevail."
It is not the first time Aldi landed in hot water over the design of some products.
In 2019, it axed a yoghurt range after Collective co-founder Amelia Harvey claimed the products looked too similar to her own. There was also a row between Heck, the sausage brand, and Aldi over similar packaging.
Last year, BrewDog posted on Twitter the similarities between Aldi’s Anti-Establishment Beer and the brand’s Punk IPA.
BrewDog’s boss said at the time it would launch a new beer called Yaldi and claimed Tesco was interested in stocking it. The two firms ended up collaborating on a product after the spat.
Carl Steele, a partner at law firm Ashfords, said: "For many years now Aldi have been selling products under brand names and using packaging that is similar to that of well-known and established brands.
"They do it so in the hope that, when coming across the Aldi product, consumers instinctively adopt the same positive feelings and emotions as they have about the branded product.
"Brand owners resent such activity and regard it as ‘free-riding’ off the brand owner’s time, cost and effort in building up and promoting their brands."
M&S has registered at least two trademarks relating to the cake. It is a key part of its partnership with cancer charity Macmillan. The retailer created a Colin product for the annual World's Biggest Coffee Morning fundraising event.
Marks will need to prove that the appearance of their cake was so well known that it had its own goodwill, meaning that consumers would recognise it as being an M&S product without any other visual cues.
If it is successful, M&S will then need to demonstrate that Aldi's Cuthbert is so similar that it is a misrepresentation to consumers.
An M&S spokesman said the company wanted to protect Colin, Connie and "our reputation for freshness, quality, innovation and value".