The Association of Convenience Stores (ACS) wants an end to the distinction between the convenience sector and supermarkets interpreted in competition regulations, to protect its 31,500 members.
ACS chief executive David Rae made the appeal in a letter to Office of Fair Trading executive director Penny Boys.
He argued that the existing two markets definition should be abolished as a reference point for considering takeovers.
He added: 'We recognise this will not at a stroke prevent further acquisitions in the convenience sector.'
An ACS spokesman said that ending the distinction would oblige the OFT to consider buyers' potential new market share of supermarkets and convenience stores together, rather than separately.
This would make the share more likely to breach the 25 per cent threshold required to refer an acquisition to the Competition Commission.
Takeovers of convenience-store groups by big grocers, such as that of Adminstore by Tesco, have made independent retailers fear the impact of competition with the giants.
The ongoing battle for control of symbol group Londis has also made smaller convenience-store groups jittery.