The Liberal Democrats have called for the introduction of an independent retail regulator to tackle the increasing dominance of the supermarkets.
The party believes a regulator will make it simpler for local authorities to judge planning applications for large stores on merit, rather than being influenced by the cost of appeals.
The party also wants reduced tax burdens on small retailers.
Local government spokesman Dan Rogerson said: "Large supermarkets can afford to squeeze local competition by undercutting prices. With more town centres turning into identikit clones, people must be given more powers to shape their communities."