The Co-op has acknowledged poor treatment of some suppliers and is acting to address the issue.

The Co-op, which faces an investigation by the Groceries Code Adjudicator (GCA), has also refunded £500,000 to suppliers involved.

The GCA revealed yesterday there was “reasonable suspicion” the Co-op had broken its rules.

It is investigating the Co-op’s delisting of suppliers, and charges imposed for comparing and assessing products to put on the shelves.

The Co-op said: “We acknowledge that we have fallen short and have been discussing the two issues raised with the GCA for some months. We have already taken decisive steps in line with our commitment to ensure the fair treatment of all of our suppliers.”

The Co-op said it has taken “steps to strengthen our systems and processes for the future”, retrained 450 staff members on how to apply the Groceries Supply Code of Practice and written to all of its 1,500 direct suppliers “to seek information on any delisting decisions that they believe may have been taken without appropriate consultation”.

The grocer has reviewed every case of a supplier being charged for benchmarking and quality control. As a result, 110 suppliers have been refunded a total of £500,000.

Co-op Food chief executive Jo Whitfield said: “We care deeply about our relationships with our suppliers and we are very sorry that in these two areas we have failed to live up to our usual high standards.

“We are already addressing the issues with the GCA and our suppliers and we hope the investigation will help bring to light any additional cases so that we can put these right as quickly as possible.”