The move would scupper plans by Asda to sweat its assets by building in mezzanine floors in stores where it cannot extend externally.
FoE claims such extensions could have as much impact on local traders, communities and traffic as opening a new store, and is pushing for an amendment to the planning Bill going through Parliament that would make internal and external extensions subject to the same restrictions.
Asda, which is planning mezzanine floors at stores in Sheffield, Cumbernauld and Govan, this year said it was disappointed FoE had singled it out. Property communications manager Simon Leonard said: "Tesco, Sainsbury, M&S, B&Q and Homebase have all adopted, in certain circumstances, mezzanine, upper floors or even basement retail formats."
For FoE to describe the flexibility in the current regime as a loophole' "misrepresents the reality of the planning process and the strong controls it places on retailers," said Leonard. "There are actually very strict restrictions about how much selling space we are allowed to operate from and even what products we sell."