A Jersey senator is calling on the competition authority to report on the island's supermarket sector and whether there is an imbalance in the market. Mike Vibert has become the latest politician to support such a plan since CI Traders took over Jersey's and Guernsey's Safeway stores in April.
Mr Vibert has also suggested a new supermarket on States-owned property might be needed.
CI Traders said that its many shops operate in competition with each other.
Best interests
Mr Vibert said having only two supermarket groups, CI Traders (which owns Jersey's Marks & Spencer, plus Le Riche and Checkers stores) and the Co-Op, was not in the island's best interests.
He said he wanted the States to consider looking for a site for a new supermarket from its own properties.
Meanwhile, the Channel Islands Co-Op has said it has seen "sensational" growth in sales following the takeover of Safeway.
Co-op boss Allan Smith, said the increase had seen Guernsey shoppers reacting more strongly than those in Jersey.
CI Traders bought the stores in Jersey and Guernsey for �51m, a day before a competition law came into force.
Tom Scott, the executive chairman, says the group's many shops will operate in competition with each other.
He said the new competition law, which could rule on whether certain firms are too dominant, may not have affected the sale, but that "it was more convenient to be done before then".