The Association of Convenience Stores (ACS) has called for the Office of Fair Trading to intervene in Tesco’s acquisition of convenience store chain Mills Group.

The ACS said the acquisition will take the number of Tesco-owned convenience stores to over 1,700. Tesco has owned the One Stop chain since 2002.

ACS chief executive James Lowman commented: “The competition authorities have repeatedly failed to grasp the implications of the continuing growth of Tesco’s shadow brand.

“The OFT allowed the original acquisition by Tesco of over a thousand stores without adequate scrutiny in 2002 and the Competition Commission failed to address the issue in the 2 year grocery market inquiry. They must not make the same mistake again; we need a full and robust investigation into the implications of the continued growth of the One Stop format.

“In the past the Competition authorities have suggested that Tesco acquisitions will bring the benefits of Tesco’s scale and buying power to consumers, however in the case of One Stop this has been proved to not be the case. “

A Tesco spokesman said that One Stop was run separately from the main chain as it had a different business model and management.

He said that its share of the convenience market was just 1.2%.