Supermarkets could be forced to charge shoppers for parking if new recommendations are enforced.
The report by the UK Commission for Integrated Transport looked at parking in different retail settings and the impact of parking charges. The study recommended redressing the imbalance of free out-of-town parking by ending free parking for supermarkets.
The Association of Convenience Stores welcomed the report. Government relations manager Shane Brennan said: "The supermarkets have an unfair advantage and we will be following up the report with the government to make sure something is done about it."