Food containing GM ingredients has been creeping into our shops recently, most often in the form of sweet treats imported from the US. However, they remain rare, to the extent that their appearance can make headline news.

In sharp contrast, GM animal feed has quietly become the norm. The majority of non-organic meat, eggs and dairy products on sale in Britain is now produced from animals fed with GM soya and maize, grown largely in Brazil, Argentina and the US.

Modified to control pests, most of the plants that produce the feed have been engineered to withstand blanket spraying with powerful weedkillers (usually glyphosate, the active ingredient in Roundup, recently classified as a probable human carcinogen).

These herbicide-tolerant monocultures are, at best, a very short-term solution. GM-sceptics are often accused of being anti-science, but promoting these crops means turning a blind eye to evolution.

You really don’t need a Biochemistry degree to understand that if you constantly expose weeds to the same one, two, or even three pesiticides, natural selection will ensure that those weeds blessed with some immunity will go forth and multiply in truly biblical proportions.

And that is exactly what is happening now, with almost half of US farms reporting Roundup resistant ‘superweeds’.

The GM industry’s answer is to up the stakes and declare all-out chemical war on nature with ‘stacked’ gene crops sprayed with a cocktail of different herbicides.

While a return to hand-weeding may make this a good time to be a chiropractor in the mid-Western US, there’s no silver lining for the smaller creatures with whom we share our planet.

Britain’s Farm Scale Evaluations found that GM farming had significant impacts on biodiversity. More recently, studies have confirmed that GM farming regimes are responsible for the devastating decline (up to 90 per cent) of the monarch butterfly, leading to calls for federal protection for this iconic creature.

In the face of such well-documented negative impacts, we must ask why the use of GM animal feed is growing, rather than receding.

Supermarkets say their suppliers can’t guarantee GM-free products any more. Indeed, unless you farm organically, it has become increasingly difficult to buy GM-free feed in Britain (although they manage to do it in Germany).

The answer lies with labelling. Consumers care about GM. In fact, the British Food Standards Agency (FSA)’s Biannual Public Attitudes Tracker (wave 9 - November 2014) published in February 2015, showed concern about GM to be rising – it’s now at the highest level ever recorded by this survey.

Another FSA study showed that two-thirds of people want comprehensive GM labelling. But foods produced from GM-fed animals do not have to be labelled, so most people don’t know they are buying GM almost every time they pick up a pint of non-organic milk, or an egg sandwich.

Low consumer awareness makes the whole thing a low priority issue for manufacturers and retailers, so there is no commercial motivation for avoiding the path of least resistance.

It may currently be difficult to pursue a completely GM-free supply chain for non-organic animal foods, but it also used to be difficult to make a soya-cappuchino that didn’t curdle, until coffee shops around the world decided it was worth the effort when their customers started demanding a dairy-free option.

So the immediate answer lies with us.

To truly exercise informed choice we need labels, but as a starting point we can all let our favourite brands – and the supermarkets that stock them – know what we think of their attitude to GM animal feed.

There may not be enough GM-free animal feed in Britain today, but I find it very difficult to believe that there aren’t enough farmers willing, ready and able to plant whatever it is that the likes of Tesco and Walmart put on the order sheet.

Liz O’Neill is the director of GM Freeze. You can contact her @GMFreeze.

For more on GM, read the April Issue of New Internationalist: Total Control – is Monsanto unstoppable?