Sainsbury's has urged the Competition Commission to apply the supermarkets code of practice to all one-stop shop grocery retailers.
Currently only the big four have to abide by the code, which lays out rules for supplier treatment.
"We believe the competitiveness of the supply chain, as well as grocery retail, would be better protected by applying the code of practice to all one-stop grocery retailers," said Sainsbury's in its latest submission to the inquiry.
Unlike Tesco, which has called for a local market to be defined by a 30-minute drive time around a store, Sainsbury's said the Commission should stick to a 10 to 15-minute drive time - but in light of Tesco's dominance it was vital to consider national as well as local aspects.
Sainsbury's also echoed Asda and Tesco's appeal for the abolition of the needs test, which planners use to decide if an area needs more grocery space. Sainsbury's wants it replaced by a market share test.