Sainsbury's has extended the relaxation of the its feeding commitments to include premium lines of meat.

The company admitted last week that it is now allowing animals that go on to supply its 'Taste the Difference' range to be fed on a diet containing genetically modified organisms. The shift means the retailer slips back into line with its competitors; almost all major supermarkets in the UK now allow their suppliers to use GM feed on animals destined for all lines except for organic products.

In April, major supermarkets including Tesco, Marks and Spencer, the Cooperative and Sainsbury's  announced that they could no longer guarantee that poultry feed used by their suppliers was free from GM ingredients, citing a shortage of certified soy. The change followeda lobbying campaign by industry groups, pressuring supermarkets to relax their commitments to GM-free poultry feed. The farming associations complained that sourcing GM-free feed was proving untenably expensive and pointed out that, for the most part, producers in other areas of animal agriculture are free to use GM feed.

On Wednesday, Sainsbury's acknowledged that "Following an industry wide availability issue it has become increasingly difficult to source guaranteed non GM feed in the short term." A spokesperson said that as a result pigs produced for the Taste the Difference fresh pork and bacon products will have been "fed on a diet which we cannot guarantee to be GM-free" since early August.

The spokesperson added, "We have taken this decision in the interests of animal welfare given the limited amount of other feed available at this time."

However, although the company allows use of GM feed for pigs used in its premium ranges, Waitrose managing director Mark Price challenged the assertions over sourcing conventional feed in June. He said the supply of non-GM soy for feed is plentiful and the price difference is minimal. Waitrose is the only UK supermarket to have upheld its poultry feed sourcing policy.

Responding to the removal of sourcing commitments earlier this year, GM-free soy producers and certifiers based in Brazil and the Netherlands challenged the major supermarkets' claims.  Ricardo Tatesuzi de Sousa of Brazilian exporter Abrange said Brazil has enjoyed, "a record soybean harvest of over 82 million metric tons, bigger than the United States' and definitely large enough to more than provide Europe's entire soy meal demand."

Tatesuzi de Sousa said, "A recent poll by the FSA indicated that 67 percent of UK citizens prefer milk, eggs, poultry and meat produced with non-GMO feed. In light of this, it is surprising that UK retailers have used the current, temporary shipping slowdown, and the consequent temporary increase in the cost of all soy (GM and Non-GM) as the basis for shifting to GM soy for animal feed.

"Certainly, mainland European retailers are responding to these consumer preferences by signalling a strong commitment to Non-GMO animal feed and by making strenuous efforts to even expand the Non-GMO soy supply chain."

In May, Augusto Freire of ProTerra, a certifier of non-GM soy in the EU, added, "The reality is that in 2012, the ProTerra Certification Programme alone made over 3.5 million metric tonnes of Non-GMO soy and soy derivatives available" and added that in 2013, this amount "will rise to over 4 million metric tonnes… of ProTerra certified soy alone," largely in response to feed commitments made by supermarket chains in mainland Europe.