Britain is facing a "massive" rise in antibiotic-resistant blood poisoning caused by the bacterium E.coli – bringing closer the spectre of diseases that are impossible to treat.

Experts say the growth of antibiotic resistance now poses as great a threat to global health as the emergence of new diseases such as Aids and pandemic flu.

Professor Peter Hawkey, a clinical microbiologist and chair of the Government's antibiotic-resistance working group, said that antibiotic resistance had become medicine's equivalent of climate change.

The "slow but insidious growth" of resistant organisms was threatening to turn common infections into untreatable diseases, he said. Already, an estimated 25,000 people die each year in the European Union from antibiotic-resistant bacterial infections.

"It is a worldwide issue – there are no boundaries," he said. "We have very good policies on the use of antibiotics in man and in animals in the UK. But we are not alone. We have to think globally." Between 2005 and 2009 the incidence of E.coli "bacteraemias" [the presence of bacteria in the blood] rose by 30 per cent, from 18,000 to over 25,000 cases. Those resistant to antibiotics have risen from 1 per cent at the beginning of the century to 10 per cent.

"Only one in 20 of infections with [resistant] E.coli is a bacteraemia, so the above data are only the tip of an iceberg of infected individuals," says a report produced by Professor Hawkey's group, commissioned by the Department of Health and the Department for Environment, Food and Rural Affairs.

Dame Sally Davies, the Government's chief medical officer, has pledged £500,000 to fund research into the threat. Drug companies have lost interest in developing new antibiotics because it is increasingly difficult to find new agents and it is not commercially viable – antibiotics are taken for a few days, compared with, say, a heart drug which may be taken for life.

"There are only so many antibiotics available and as we lose them it becomes more and more difficult to replace them," Professor Hawkey said.

The rapid rise in E.coli blood poisoning is thought to be linked with the ageing of the population. E.coli is a common cause of urinary-tract infections but may also cause wound infections following surgery or injury. These are regarded as minor conditions, but if they became untreatable they would be life-threatening.

E.coli infections pose a much bigger problem than MRSA because the bacterium is more common. Only one in 10 people is a carrier of MRSA, but E.coli is present in everyone. "Those who get ill [with E.coli] are rare – but because it is so common it is a big problem," Professor Hawkey said.

Using standard antibiotic regimens, there is a one in 10 chance that treatment of an E.coli infection will fail because the bug is resistant. But, as numbers of resistant infections rise, there will be increasing pressure to use more powerful antibiotics, called carbapenems, which are the last line available. And resistance to those is already emerging. "In the last two or three years we have seen [organisms] develop which destroy carbapenems. That is a great worry," Professor Hawkey said. The warnings follow increasing reports from Europe of patients with infections that are almost impossible to treat. In November, the European Centre for Disease Control and Prevention (ECDC) said up to 50 per cent of cases of blood poisoning with the bacterium K.pneumoniae, a common cause of urinary and respiratory conditions, are resistant to carbapenems in some countries.

Across Europe, the percentage of carbapenem-resistant K.pneumoniae has doubled from 7 per cent to 15 per cent, the ECDC said. Marc Sprenger, the director, said: "The situation is critical. We need to declare a war against these bacteria."

Meanwhile, the UK Health Protection Agency warned doctors in October to abandon a drug usually used to treat a common sexually transmitted disease because it was no longer effective. The agency said that gonorrhoea – which caused 17,000 infections in 2009 – should be treated with two drugs instead of one.

Explained: how bugs adapt to beat antibiotics

Bugs are like all other life forms: they must adapt to survive. Unlike human beings, however, for whom evolution is measured in millennia, reproduction is so rapid among bacteria that they can change in months or years.

With the introduction of a new antibiotic, natural selection goes to work. Most bacteria are killed by the new drug but the natural variation that occurs in any species means a few examples may, by chance, have some quirk in their genetic structure that allows them to survive.