The Commerce Commission has confirmed it will formally investigate allegations of anti-competitive behavior towards suppliers by Countdown and assured anonymity for those who require it.
In a statement, the Commission said its investigation was expected to take some months and it would be seeking a wide range of information from groups in all areas of the supermarket sector.
The inquiry appears to be limited to Countdown. The Commission has urged anyone with relevant information to contact it and undertaken to give anonymity to those who request it unless consent is given to disclose it or they are required to do so by law.
"If confidentiality is a concern then it should be raised when first contact is made with the Commission."
It has been considering the investigation since Labour MP Shane Jones lodged a complaint a week ago and used Parliamentary privilege to allege Countdown was forcing some suppliers to make retrospective payments to boost profit margins.