Marks and Spencer has launched legal action against Aldi over a claim that the discount supermarket is infringing the trademark of its Colin the Caterpillar cake.
M&S has lodged an intellectual property claim with the High Court this week relating to its rival’s Cuthbert the Caterpillar product.
It argues that the similarity of the Aldi product leads consumers to believe that they are of the same standard and allows Cuthbert to "ride on the coat-tails" of the M&S cake’s reputation.
M&S wants Aldi to remove the product from sale and agree not to sell anything similar in the future.
Colin the Caterpillar, a sponge cake with milk chocolate and buttercream, topped with chocolate sweets and a smiling white chocolate face, was launched around 30 years ago.
Its appearance has been substantially unchanged since around 2004, though there have been special adaptations for events such as Halloween and Christmas.
There have also been spin-offs such as Connie the Caterpillar, which was promoted around Mother’s Day.
Colin is also part of M&S’s partnership with cancer charity Macmillan.
The retailer has created a Colin product for the charity’s annual World’s Biggest Coffee Morning fundraising event.
M&S has three trademarks relating to Colin, which the retailer believes means Colin has acquired and retains an enhanced distinctive character and reputation.
A spokesman said: "Because we know the M&S brand is special to our customers and they expect only the very best from us, love and care goes into every M&S product on our shelves.
"So we want to protect Colin, Connie and our reputation for freshness, quality, innovation and value."
Asked why M&S was taking action over this product in particular, a spokesman said it was taking "a targeted approach to protect our brand assets".
He added: "We have got significant concerns about this product."
Aldi declined to comment. Cuthbert is not currently on sale.