Following Tesco’s announcement earlier this week that it is delisting a number of core John West lines as part of its shift towards only selling sustainably caught seafood, a report by The Times suggests that Sainsbury’s and Waitrose are threatening a similar move.

Tesco’s decision to delist 20% of John West products sold in its stores this month came after the retailer launched a review to ensure all the tuna on it shelves – including branded products – met its requirements, coming from pole and line, FAD-free or Marine Stewardship Council (MSC) certified fisheries.

The Times said that Sainsbury’s has also warned John West that if it did not improve its practices by 2018 it would “act accordingly”. A company spokesperson is quoted as saying: “We’re the UK’s leading retailer of sustainable fish and we expect our suppliers to take a responsible approach to sourcing.”

Meanwhile, Waitrose has issued an ultimatum to John West, asserting that all its canned tuna must be caught by pole and line, or MSC certified, by the end of next year.

In immediate response to Tesco’s announcement, John West said that the delisting of its products was not just about sustainability. A spokesperson for the firm said: “Tesco’s review of the fish products it stocks, which has resulted in approximately 20% of the John West range being withdrawn, was driven by commercial negotiations as much as sustainability considerations.”