Tougher regulations on the use of antibiotics on farm animals are needed as a matter of urgency as part of Brexit negotiations, campaigners and politicians have urged, after fresh revelations of superbugs found in UK supermarket meat products.

E coli germs resistant to all of the currently used antibiotics have been found in UK supermarket meat, with a quarter of chickens found to contain the deadly superbugs, in research from Cambridge University.

The discovery has been strongly linked to the overuse of antibiotic medicines among farm animals, including chickens and pigs.

Overuse of antibiotics among farm animals fosters the development of resistant germs, which can then infect people and cause serious illness. The Guardian has previously revealed strong evidence of another “superbug” resistant to antibiotics - MRSA - found in nearly one in 10 samples of UK supermarket pork.

Current curbs on antibiotic use on UK livestock are among the regulations under discussion as the government prepares for Brexit. Campaigners fear that these rules will be watered down under pressure from trading partners, with potentially catastrophic results for UK consumers.

Peter Melchett, policy director of the Soil Association, told the Guardian: “We want the government to ban all routine use of antibiotics on groups of entirely healthy animals, to phase out the use of critically important antibiotics [on animals] and ensure that last-resort antibiotics are only used to treat individual farm animals, and only if no other antibiotics are found to be working. We want to see this enacted whether we are in the EU or out of it.”

Philip Lymbery, chief executive of Compassion in World Farming, said: “This new research makes it clear that the UK government must take urgent steps to save our antibiotics and avert a post-antibiotic era. The government must put in place policies to ban the routine preventative use of antibiotics in groups of entirely healthy animals.”

He also called for the use of certain critical antibiotics, regarded as the last line of defence against devastating human illnesses, to be kept from routine use in animals in order to retain their efficacy.

“If we continue to sacrifice animal welfare in the name of cheap meat, future generations will pay the price for a long time to come,” he said.

Important trading partners such as the US and China have much lower animal welfare standards, and more lax controls on the use of antibiotics on their farms, than the UK and the EU. UK trade negotiators are likely to be under pressure to accept lower standards as a result, and more than 80 civil society organisations have called for the government to resist such attempts.

E coli can kill or cause serious illness, and the potency of the antibiotics used to counter it is being eroded, which scientists have linked to the over-use of antibiotics in treating farm animals. The discovery of food products on general sale in the UK harbouring resistant bugs has raised concern that current regulations on the use of antibiotics are insufficient to protect consumers.

Under current rules, little oversight is kept of the use of antibiotics on individual farms. The UK’s Department of Environment, Food and Rural Affairs keeps track of the volume of such drugs used overall in farming each year, but without keeping records of individual use and the reasons for it, leaving this to vets.

Vets can find themselves under pressure, from farmers anxious to ensure they can continue to sell their livestock, and because they make money from prescriptions as well as advice.

Even the current regulations - regarded as too weak by campaigners - are now under threat, as the government prepares for the “bonfire of red tape” on farming, that was called for by Brexiteers.

Antibiotics have been at the forefront of the war against disease since the middle of the last century, but scientific developments have failed to keep up with the progress of the bugs. When antibiotics are used, most of the germs they target are killed, but a few can remain that evolve to develop and propagate resistance.

When antibiotic medicines are over-used, for instance in healthy people or farmyard animals not at risk of disease, a higher proportion of the bugs develop this resistance, leading to larger populations of lethal superbugs.

The discovery of germs resistant to E coli in many supermarket foods follows on revelations by the Guardian that MRSA-resistant bacteria was present in about a tenth of UK supermarket pork products. MRSA is another antibiotic-resistant “superbug” that can be fatal to vulnerable people, such as the very old and young, and can cause severe illness even in healthy people.

The government could help to reward farmers with high animal welfare standards by blocking cheap foreign imports from countries with lower standards under future post-Brexit trade deals, added Tracy Worcester, director of Farms Not Factories, a pressure group.

She said: “Livestock from high animal welfare farms very rarely need to be given antibiotics. Farmers and the government could agree the farm gate price that reflects production costs. Cheap foreign imports could be blocked and all public services could procure meat produced with high animal welfare labels.”

She called on people to write to supermarkets to urge them to crack down on antibiotic use among their suppliers, and to take to social media on the issue.

Molly Scott Cato, an MEP for the Green arty, said the party was strongly in favour of curbing routine antibiotic use in farming and monitoring the use of powerful drugs as a last resort. She said: “We need to ensure that human and animal health is put before the interests and profits of industrial-scale farming. The emerging EU legislation on the use of antibiotics in farming is setting a global standard for the sensible use of these drugs that are so essential for human health. It is vital that the UK adopt the highest standards that emerge from this legislative process.”

She added that farming subsidies to be paid for by UK taxpayers, after Brexit, must also only be handed out on the basis of strong health and environmental standards. “We need to ensure any new subsidies for agriculture should prioritise a transition away from intensive farming and towards an environmentally and ecologically sustainable agricultural industry,” she said.