Routine operations could become deadly "in the very near future" as bacteria evolve to resist the drugs we use to combat them. This process could erase a century of medical advances, say government doctors in a special editorial in The Lancet health journal.
Although the looming threat of antibiotic, or anti-microbial, resistance has been known about for years, the new warning reflects growing concern that the NHS and other national health systems, already under pressure from ageing populations, will struggle to cope with the rising cost of caring for people in the "post-antibiotic era".
In a stark reflection of the seriousness of the threat, England's deputy chief medical officer, Professor John Watson, said: "I am concerned that in 20 years, if I go into hospital for a hip replacement, I could get an infection leading to major complications and possible death, simply because antibiotics no longer work as they do now."
About 35 million antibiotics are prescribed by GPs in England every year. The more the drugs circulate, the more bacteria are able to evolve to resist them. In the past, drug development kept pace with evolving microbes, with a constant production line of new classes of antibiotics. But the drugs have ceased to be profitable and a new class has not been created since 1987.
Writing in The Lancet, experts, including England's chief medical officer, Dame Sally Davies, warn that death rates from bacterial infections "might return to those of the early 20th century". They write: "Rarely has modern medicine faced such a grave threat. Without antibiotics, treatments from minor surgery to major transplants could become impossible, and health-care costs are likely to spiral as we resort to newer, more expensive antibiotics and sustain longer hospital admissions."
Strategies to combat the rise in resistance include cutting the amount of antibiotics prescribed, improving hospital hygiene and incentivising the pharmaceutical industry to work on novel antibiotics and antibiotic alternatives.
However, a leading GP said that the time had come for the general public to take responsibility. "The change needs to come in patient expectation. We need public education: that not every ill needs a pill," said Dr Peter Swinyard, chairman of the Family Doctor Association.
"We try hard not to prescribe, but it's difficult in practice. The patient will be dissatisfied with your consultation, and is likely to vote with their feet, register somewhere else or go to the walk-in centre and get antibiotics from the nurse.
"But if we go into a post-antibiotic phase, we may find that people with pneumonia will not be treatable with an antibiotic, and will die, whereas at the moment they would live.
"People need to realise the link. If you treat little Johnny's ear infection with antibiotics, his mummy may end up dying of pneumonia. It's stark and it's, of course, not direct, but on a population-wide level, that's the kind of link we're talking about."
There are no reliable estimates of what resistance could cost health systems in the future, but the European Centre for Disease Prevention and Control believes that €1.5bn (£1.2bn) a year is already being spent on health problems associated with antibiotic resistance in Europe.
Joanna Coast, professor of health economics at the University of Birmingham, said that the problem of resistance had the potential to "affect how entire health systems work".
Professor Coast added: "We don't know how big this is going to be. It's like the problems with planning for global warming. We know what the costs are now but we don't know what the costs will be into the future.
"Much of what we do in modern health system relies on us having antibiotics. We need them for prophylaxis for surgery, for people having chemotherapy for cancer. The worry is that it might make big changes to how we run our health system."
Antibiotics are also used in vast quantities in agriculture, fisheries and by vets, the resulting environmental exposure adding to bacterial resistance, with further consequences for human health.
Experts say that to meet demand without increasing resistance, drug companies will need to find new ways of financing antibiotic development that are not linked to expectations of large volume sales. Global health authorities such as the World Health Organisation have also warned that global drives to reduce antibiotic use must not harm access to life-saving drugs in poorer countries.
Writing in The Lancet, Professor Otto Cars of Uppsala University in Sweden, and one of the world's leading experts on antibiotic resistance, said: "Antibiotic resistance is a complex ecological problem which doesn't just affect people, but is also intimately connected with agriculture and the environment.
"We need to move on from 'blaming and shaming' among the many stakeholders who have all contributed to the problem, towards concrete political action and commitment to address this threat."