Most of the UK’s leading supermarket chains are making “significant progress” in reducing antibiotics in farming, but Iceland, Asda and Aldi have been named as falling behind in a new study.

Iceland was found to be the only major chain to have no publicly available policies on antibiotic use in its supply chain and no strategy in place to reduce the use of the vital medicines.

Asda says it does not support the routine preventive use of antibiotics, but publicly lists no restrictions on such use, other than the UK’s minimum legal requirements, which campaigners say are insufficient. Aldi says publicly that it recommends that routine use should be avoided by its suppliers.

“More and more supermarkets are at last collecting some data and all but Iceland have some sort of strategy in place – that is progress,” said Cóilín Nunan, a scientific adviser to the Alliance to Save Our Antibiotics, which carried out the research. A similar report in 2017 found most supermarkets were falling short of best practice.

The UK’s other leading supermarket chains in the survey – Co-op, Lidl, Marks & Spencer, Sainsbury’s, Tesco, Waitrose and Morrisons – have all put in place bans on routine preventive dosing of livestock.

Waitrose was named in the study as leading the pack, with “the most comprehensive antibiotic policies”. M&S and Tesco were next-best.

The overuse of antibiotics is linked to the rise of superbugs and can also contribute to the evolution of dangerous viruses, similar to the coronavirus.

Top medics, including England’s former chief medical officer Dame Sally Davies, have repeatedly warned that the rampant overuse of antibiotics is threatening a global disaster, as it gives rise to resistant germs which will mean common illnesses become untreatable.

A spokesperson for Iceland said the retailer was revising its policy “in the coming weeks” to include a ban on the routine use of antibiotics, restrictions on critically important antibiotics, and a new strategy to reduce antibiotic use among its suppliers. “We are well aware that antibiotic overuse among farmed animals is an important issue for human health [and] have an established technical policy for Iceland’s own label suppliers. We have always prohibited the use of growth promoters,” said the company.

Aldi said it had moved to ban the preventive use of antibiotics after being contacted several months ago by the Alliance to Save Our Antibiotics for the purposes of the report. Asda said it complied with UK regulations, and added: “We publish all use of antibiotics on our website each year for complete transparency.”

Routine preventive dosing of healthy animals with antibiotics is also linked to the rise of potentially fatal viruses. Although the coronavirus recently discovered in Wuhan may have come from wild animals, similar outbreaks of viral diseases that spread to people – such as bird flu and swine flu – have been directly linked to intensive farming.

Antibiotics are not used to treat viruses, but overusing antibiotics allows farmers to keep animals much more densely packed than would otherwise be possible, and in these conditions new viruses can rapidly emerge and flourish.

“We don’t know where the coronavirus has come from – it could have come from wild animals,” said Nunan. “We do know that the way antibiotics are used in intensive farming allows more animals to be kept in close proximity and in those conditions we know viruses can evolve and spread. So there is an indirect link.”

The report also found that Waitrose and M&S were the only supermarkets that did not permit their suppliers to use colistin, an antibiotic of last resort used to treat life-threatening infections in people. The World Health Organization has urged governments to restrict its use to human health.

The Alliance to Save Our Antibiotics is also urging the government to reinforce the UK’s farming antibiotic regulations after Brexit. “Preventive mass medication of livestock is very widely practised around the world and it does help to lower meat prices,” said Nunan. “Unless you get a ban on the importation of meat and dairy that have been treated with preventive mass medication, [British] farmers will have that competition.”