The Association of Convenience Stores has suggested ditching the Office of Fair Trading's current two-market definition for a new one that distinguishes between wholesale and retail.

The ACS argues that the OFT's assertion that the grocery market consists of one-stop and top-up shops should be replaced with a definition comprising the national wholesale market for the purchase and distribution of products, and separately the local, consumer-facing retail market.

The definition has been adopted to highlight two tiers of problems - those affecting the national supply chain and those involving local competition between individual retailers.

The proposal was published in the ACS's full submission to the Competition Commission's grocery market inquiry, which was made public this week.

The ACS said it would follow up the submission with further papers, including an outline of supermarket abuse of the retail planning system, later this month.

It has also promised to provide modelling exercises to ensure the interests of unaffiliated independent retailers are represented.

John Murphy, director general of the Federation of Wholesale Distributors, said: "The competition authorities have not been effective in tackling the consequences of the growth of the major multiples and this inquiry must mark a watershed."