An official investigation is to be launched in Britain into practices at supermarket giant Tesco, including any delays in payments to suppliers.
The country’s Groceries Code Adjudicator, Christine Tacon, announced the move, saying she had formed a "reasonable suspicion" that the retailer has breached the Groceries Supply Code of Practice.
She said she took the decision after considering information submitted to her relating to practices associated with the profit over-statement announced by Tesco last September.
She has discussed the practices with Tesco and said she now needs more information from direct suppliers and others to determine what further action to take.
The role of the Adjudicator was set up in 2013 to regulate the relationship between the ten largest retailers and their suppliers.
The investigation, the first to be held, is expected to take up to nine months and the Adjudicator has called for evidence to be submitted by 3 April.
It will cover the conduct of Tesco from 25 June 2013 - when the GCA was created - to 5 February this year, and will focus on delayed payments to suppliers.
The probe will also look at whether suppliers have been required to make payments to Tesco in order to get their product more prominently displayed in stores.
Ms Tacon said: "This is the first investigation I have launched and it is a significant step for the GCA.
"I have taken this decision after careful consideration of all the information submitted to me so far.
"I have applied the GCA published prioritisation principles to each of the practices under consideration and have evidence that they were not isolated incidents, each involving a number of suppliers and significant sums of money."
A Tesco spokesman said: "We will continue to co-operate fully with the GCA as she carries out her investigation and welcome the opportunity for our suppliers to provide direct feedback."
"Following our announcement last September regarding commercial income, we have worked with her to identify any relevant GSCOP issues. An internal review we carried out and shared with the GCA identified some areas of concern.
"We have taken action to strengthen compliance and, as we have announced, we are changing the way we work with suppliers.”