The only redeeming feature of the overbearing power of supermarkets is that they can use their muscle for good.

A perfect opportunity for such intervention is now presented by the British Poultry Council (BPC), which is toying with the idea of dumping its guarantee that members use only non-GM poultry feed. The BPC says that this “unsustainable” rule is “imposed by retailers”. It’s too hard to source non-GM soya, it complains.

This is nonsense. 40% of Brazilian soya is certified non-GM, so if poultry producers can’t get their act together to source some from the perfectly efficient companies importing it, they clearly aren’t trying.

Any fool can see that BPC producers would be slitting their own throats if they went down the GM path. Exposés by Jamie and Hugh of sordid UK broiler sheds left the British chicken industry with a chronic PR problem. Add a further GM taint, and chicken could become Public Meat Enemy Number One. Why on earth would retailers stand back and let that happen?

These days, food production needs to be seen to be clean and green. Note that Sweden just decided to use only GM-free feed for its pigs, closing off the last route of GM feed into its food chain.

Why? Because the GM story just keeps getting worse.

Scientific evidence that GM crops have negative effects on laboratory animals damage to the immune system, kidneys and liver, and negative impacts on fertility is stacking up. Understandably, consumers may feel that if GM foods aren’t that great for their pet rodents, they themselves would rather not eat any.

Far from heaping food on the Third World plate, shocking evidence is emerging from charities such as Christian Aid that in countries like India, buying GM seed has forced poor farmers into a spiral of debt, pesticide pollution and crop failure. Some estimates suggest that thousands of farmers there have committed suicide as a result.

The BPC could try to bury its unpopular volte face by signing up to the Roundtable on Responsible Soya, which belies its name by permitting the use of GM soya.

But then, the RTRS is being outed by environmental groups as a crude food industry exercise in greenwashing. Better the supermarkets have a quiet word with the BPC now, before it makes a catastrophic error.