Pressure is mounting on the Competition Commission to rethink its view that the number of independent c-stores in the UK is on the up, after serious flaws were exposed in the scope and interpretation of the data.

As part of its groceries inquiry, the Commission issued a working paper last week, arguing that the growth of c-stores owned by major grocery retailers was "mirrored by the growth of non-affiliated independent c-stores".

The statement came under fire from c-store leaders who pointed out that the data on which it was based - research by Experian Goad - covered 1,115 town centres but not neighbourhoods, estates and villages, traditionally the heartland of the convenience sector.

Knowledge Store/IGD data - produced by The Grocer's owner Wm Reed Publishing, and based on the entire grocery market - presented a more comprehensive view of the market, they said, and showed the number of non-affiliated independents fell 5.3%.

An analysis this week by the Knowledge Store demonstrated how incomplete the picture provided by the Experian Goad research is.In a study of Farnborough, Knowledge Store/IGD listed 31 c-stores, Experian Goad recorded five.

The ACS warned the Commission it would have a "one-dimensional view" of the market if it did not look beyond town centres.

The Commission said it would look into why the two sources produced such differing results.