Co-op appears to be the first store to display the chocolates, and a number of people have taken to social media to express their bemusement.
The treats are being a stocked more than three months in advance of the day itself, with Easter falling on April 1 in 2018.
Co-op defended the move, saying figures show “many customers will buy chocolate eggs as soon as they can.”
But it has come under plenty of stick, with one Twitter user fuming: “How the heck can you justify stocking Easter Eggs while it’s still Christmas???!!!!”
Fiona McDonald wrote: "Is this a joke? It's Boxing Day and you have Easter eggs on your shelves!"
Another person said: “My Grandparents local shop has Easter eggs in on 27th December.
"I had to take a photo to prove I'm not going completely insane. I just can't!!!”
Jackie Lynch wrote: “And now I've seen it all. Easter eggs on sale on 27th December. What were you thinking @coopukfood?!”
Philip Joel added: “I love Easter holidays as much as anyone else but selling Easter eggs on the 27th December @coopukfood is a joke.”
Co-op said in a statement: “As a convenience retailer, our stores often have limited backroom space which means products go on-shelf when space appears.
“Sales figures also show that many customers will buy chocolate eggs as soon as they can.”
