Here is a news story that could determine whether you live or die. Many of the world's scientists are warning that one of the mightiest weapons doctors have against sickness is being rendered useless – so a few people can get richer, for a while. If they aren't stopped soon, the World Health Organisation warns we are facing "a doomsday scenario of a world without antibiotics". It will be a world where transplant surgery is impossible. It will be a world where a simple appendix operation will be as routinely lethal as it was in 1927, before the discovery of penicillin. It will be a world where pneumonia and TB and gonorrhea are far harder to deal with, and claim many more of us. But it's a world that you and I don't have to see – if we act on this warning now.

As the scientists I've interviewed explain it, antibiotics do something simple. They kill, slow down or stall the growth of bacteria. They were one of the great advances of the 20th century, and they have saved millions of us. But they inherently contain a problem – one that was known about from very early on. They start an arms race. Use an antibiotic against bacteria, and it kills most of it – but it can also prompt the bacteria to evolve a tougher, stronger, meaner strain that can fight back. The bacteria is constantly mutating and dividing. The stronger the antibiotic, the stronger some bacteria will become to survive. It's Darwin dancing at super-speed.

So the more we use antibiotics, the more we lose them. It's a battle played out on human bodies and in human wounds, with sky-high stakes. In many developed countries today, MRSA kills more people than Aids. The obvious conclusion, then, is that we should use antibiotics sparingly, and only when they are really needed to treat the sick. But in one crucial area we are doing the exact opposite – for the sake of a few people's profits.

In the United States, Latin America, and Asia, animals being farmed for meat and milk are being automatically given antibiotics in their food all day – irrespective of whether they are healthy or sick. It's like slathering your child's Cornflakes with antibiotics, all year round. Some 80 per cent of all antibiotics in the US go straight into farm animals. This speeds up the race massively. It's like taking bacteria to the gym and giving them a constant work-out – and then unleashing them on the rest of us.

You can see how this process makes bacteria stronger and tougher – and at work on humans – in a startling study by Professor Barry Levy in the New England Journal of Medicine. His team went to a chicken farm where antibiotics had not been used before, and started to put the antibiotic tetracycline into their feed. Before the start of the experiment, there was no tetracycline-resistant bacteria on the farm. Within two weeks, 90 per cent of the chickens were excreting tetracycline-resistant organisms. Even more strikingly, half of all the humans living on the farm were by then excreting tetracycline-resistant bacteria too.

This process partially explains the evolution and spread of many superbugs. Only a fortnight ago, a new strain of MRSA was found in British milk that could be transmitted to human beings. To some degree this arms race is an inevitable part of nature – but our factory farms are massively artificially accelerating it. They are bringing the day when antibiotics won't work much closer.

Why? Why would factory farms automatically feed antibiotics to healthy animals, given the obvious risk? If you cram animals together, give them little room to move, and make them grow and produce far beyond the level they would in natural circumstances, they will routinely get ill – and they do. It is cheaper for their owners to simply automatically and pre-emptively drug them all, than to try to treat their illness individually, or to create an environment where sickness is not standard.

The animals in these factory farms can become reservoirs of stronger superbugs. Sometimes it spreads to us through contamination of raw meat, but more often it filters out through workers who have contact with the animals. Dutch pig farmers are 760 times more likely to be carrying pig-MRSA than the rest of the population. This story ends eventually with the death of antibiotics – and routine operations becoming deadly once more.

We always knew factory farming was a scar on our conscience, but it turns out it is also an urgent threat to our health. Of course, factory farming is not the only source of growing antibiotic resistance. Doctors have been overprescribing them, and patients have too often not been taking their full course, enabling tougher bacteria to survive and thrive. But this is the most egregious cause.

A few years ago, it looked like the European Union had taken the lead, by banning the routine use of some types of antibiotics simply to promote the growth of animals. But research published this week by the Soil Association suggests farmers are sidestepping the real issue. The prescription of modern cephalosporins, the antibiotics which are most widely believed to promote stronger variants of MRSA in animals and humans – has quadrupled in the past decade in Britain. Why? They are advertised to farmers, who are under greater pressure than ever to get more and more out of their herds because supermarkets have ratcheted up the pressure for quick profit. Decent small farmers who want to resist these trends find themselves out of business.

The former chief medical officer Liam Donaldson says this over-prescription is so dangerous to us all it should be banned. Yet David Cameron's Government ignored the official recommendation from its own veterinary advisers to take even the much milder step of banning the advertising of antibiotics to farmers.

It might seem strange that governments all over the world are taking such a gamble with public health, in the face of the best scientific advice. But Big Agriculture has armies of lobbyists and open chequebooks, while the people trying to protect the public have only the facts and reason and truth on their side. The squandering of life-saving antibiotics is one example of a bigger trend hijacking global politics. Small groups of rich people, determined to maximise profits, are buying or bamboozling politicians into serving their interests and into ignoring the interests of the vast majority of the population. This is the trend that is making it so hard to (say) reregulate the banks to prevent another global crash, or prevent the unravelling of the climate.

It doesn't have to be this way. The majority of the population can organise and shout louder than these self-interested juntas of profit. There are inspiring examples. In Lincolnshire, there were plans to import the first US-style mega-farm into this country by a group of tycoons who claimed their cows "do not belong in fields". But public pressure forced the Environment Agency to investigate, and the plans to be abandoned. Fighting back on issues like this works – and we need to step it up.

Otherwise, the history books – written by people more vulnerable to bacteria than you and I have ever been – will record something startling. Our demand for cheap meat turned us, in turn, into cheap meat.