Health and animal welfare campaigners analysed 10 UK caterers' policies and found a lack of a ban meant controls on antibiotics could be weak or absent.

The government, caterers and suppliers say voluntary measures are effective.

The Department for Environment, Food and Rural Affairs (Defra) points to a 55% drop in antibiotic use in food-producing animals since 2014 and an 83% decrease in the use of antibiotics most critical for human use.

Caterers who supply the public sector said they were committed to reducing unnecessary antibiotic use in animals farmed for food.

There is a global drive to reduce the use of antibiotics, in both human medicine and agriculture, to tackle the rise of 'superbugs' - strains of bacteria that can no longer be treated by certain drugs.

The Alliance to Save Our Antibiotics (ASOA) assessed the publicly-available food procurement policies of 10 of the UK's leading caterers supplying the NHS, the education sector, care homes and prisons.

In a report released on Thursday, it claimed the firms had either "weak or non-existent" policies on antibiotic use.

It said the companies were "lagging well behind" the standards set by supermarkets and elsewhere in the commercial food sector.