It has been shared 433,156 times in the last seven days through Facebook, Twitter and blog posts.
The spot follows a British soldier who connects with his German counterpart, who then slips a bar of chocolate in his pocket. It was directed by Ringan Ledwidge through Rattling Stick.
It marked the supermarket’s 20-year relationship with the Royal British Legion.
Since its release on 12 November, "Christmas is for sharing" by Abbot Mead Vickers BBDO has been shared 447,506 times.
Other Christmas ads are also proving to be popular, with the John Lewis ad "Monty the Penguin" by Adam & Eve/DDB making it into second place with 133,653 shares over the past seven days.
The third most shared ad of the week moves away from the festive ads dominating the top of the list. Turkish Airlines "Drogba vs Messi: #EpicFood" by Crispin Porter & Bogusky London was shared 108,020 times in the past week.
Burberry’s Christmas ad "from London with love" by Burberry took fourth place this week with 100,219 shares.