Groceries Code Adjudicator Christine Tacon has warned she is “warming up” for her first investigation - into packaging and design charges.

Suppliers have complained of excessive charges for photography and packaging design, which they said quickly added up as a result of frequent changes to design. In the past two years, charges for photographs had increased four-fold in some cases, they told the adjudicator.

At the GCA annual conference on Monday, Tacon said she had initially thought tackling the issue would be an easy win. She said she had approached retailers and asked them to voluntarily agree suppliers should only foot the bill for one redesign a year and to pay themselves for any subsequent changes.

However, she had been unable to reach an agreement with retailers, she said. Although she would continue to press them to make voluntary commitments, if this failed it could become the subject of her first investigation.

“I am getting so much conflicting evidence from retailers and suppliers,” she said. “It is an area where I am warming up to an investigation.”

Packaging and design charges potentially breach GSCOP on two counts - by obliging suppliers to contribute to marketing costs and by requiring them to obtain goods and services from a third party.

At the conference, Tacon also hailed the success of the new voluntary approach to “forensic auditing”. With the exception of Waitrose and Sainsbury’s, the 10 retailers covered by the code had agreed to slash the time they backdate demands for money from six years to two.

Tacon said the agreement showed it was possible to achieve progress without resorting to time-consuming investigations or antagonism.

Read this: Adjudicator Christine Tacon on the challenges ahead