The dish, made with broccoli, peas, avocado and quinoa, has been on the group’s menus in various forms since 2004.
But the ASA ruled that the health claims implied by its name were not backed up by authorised evidence.
Leon argued that the salad was exempt from current marketing laws as the brand name existed before the regulations came in to force in 2005.
It claimed that the rules did not apply as it had used the name ‘Superfood Salad’ on products since summer 2004.
However, the ASA said that the ingredients of the pre-2005 salads varied and that consumers would not realise ‘Superfood Salad’ was a brand name.
The watchdog ruled that the ‘superfood’ term could not be used again in its current form.
In a ruling, the ASA wrote: “We told Leon Restaurants Ltd not to make references to general benefits of food for overall good health or health-related well-being in brand names unless those claims were accompanied by a permitted health or nutrition claim.”
But Leon branded the ruling a ‘shame’ and said it would be seeking an independent review.
The company said in a statement: “We created the original ‘Superfood Salad’ in 2004, and it has since inspired many others. It would be a shame if the Leon ‘Superfood Salad’ had to change its name. We respect the ASA process, and will be taking the next step of applying for an independent review.”