M&S refuses to yield in copycat row with Aldi over caterpillar cake

It's one of Britain's more unusual legal wrangles, involving a chocolate cake in the shape of a caterpillar and two of the country's best-known retailers.

Marks and Spencer has threatened its cheaper supermarket rival Aldi and the high-street giants have traded barbs on social media.

M&S' food store chain last week lodged an intellectual property claim with the High Court in defence of its trademarked chocolate-iced sponge character Colin the Caterpillar.

It argued that the German supermarket chain Aldi was misleading customers with its "Cuthbert" cake, which is also sold in green packaging, and wants it to desist from further sales or similar products.

Aldi on Tuesday urged M&S to drop the legal action, tweeting: "Can Colin and Cuthbert be besties?"

It defiantly vowed to sell a limited-edition version of the cake to raise funds for cancer charities.

M&S tweeted back: "We just want you to use your own character", proposing "Kevin the Carrot Cake".

Many have pointed to the legal claim's selective nature, given that at least six other UK supermarkets sell caterpillar cakes similar to the M&S one, while Aldi's version is the cheapest.

Aldi suggested Tuesday that all the supermarkets selling similar cakes - with names such as Curly, Clyde, Charlie, Morris and Wiggles - should work together to "raise money for charity, not lawyers".

Waitrose tweeted that its Cecil cake was a "caterpillar of the community...count us in!"

M&S Food, specialising in high-end ready-made dishes, apparently fears an association with discount chain Aldi will leave a nasty taste in consumers' mouths.

The store is famous for its breathy slogan: "This is not just food, this is M&S food".

Aldi parodied this: tweeting "This is not just any court case, this is #FreeCuthbert." It also posted an image of Cuthbert behind bars.

The Colin cakes have been in production since 1990, The Financial Times reported.

The broadsheet quoted legal experts as saying the case hinged on whether Aldi's roly-poly birthday treat was close enough to the M&S product to confuse customers.

Colin is a popular line for M&S, including themed Easter eggs and cupcakes.

He has a female equivalent called Connie who is decorated with flowers.

The Sun reported that in a taste test, M&S' "dry" and "sickly sweet" Colin crawled in behind Waitrose's Cecil.

But the newspaper could not get a hold of Colin, as he had been off the shelves since mid-February.