A row over food labelling has prompted supermarket Sainsbury's to suspend its membership of trade body the British Retail Consortium (BRC).
Sainsbury's wants 'traffic light' labels on food
The group said it made the move after BRC chief Kevin Hawkins appeared to back rival Tesco's stance on the issue.
Tesco is currently opposed to Food Standards Agency plans to introduce a "traffic light" labelling system.
But Sainsbury's backs proposals to introduce a red, amber and green coding system to show fat and salt levels.
Sainsbury's confirmed it had suspended membership of the trade body until 30 April.
The move comes just as the Competition Commission is launching its latest inquiry into the grocery sector.
However, the BRC said the matter was a "private one" between itself and the supermarket group.
"We are currently in dialogue with Sainsbury's to clarify the issues and expect to resolve the matter very soon," the group added.
The UK's third largest supermarket supports government plans to introduce a traffic light labelling system to indicate whether a food has high, medium or low levels of fat, saturated fat, sugar and salt.
"This follows concern about how the BRC is able to represent members effectively on issues where they hold significantly differing views," a statement from the group said.
"We have had concerns for a while, but the issue was highlighted most recently following the Food Standards Agency announcement on food labelling."
Despite claims of a rift Sainsbury's is widely expected to return to the trade body when its period of suspension ends.
"This is a temporary thing, the BRC does need Sainsbury's - it would be a weakened body without it," Nick Gladding retail analyst at Verdict said.
He added that Sainsbury's move was a tactic they were using to make a point and get its views on the food labelling issue heard.
Sainsbury's decision is the latest in a series of disagreements that have dogged the BRC as it prepares to defend the supermarkets to the Competition Commission inquiry.
Media reports have suggested that Asda could follow Sainsbury's lead, a move that could deal a potentially fatal blow to the BRC.
A spokesman for Asda told the Independent that the group was "concerned" about the BRC's response to news that competition watchdogs will be investigating the sector.
However, the BRC said it had yet to receive any complaints from Asda about its performance.