The Soil Association wants virginiamycin imports from Australia to be stopped immediately to prevent it entering the food chain.
The Soil Association has called on the Government to stop the use of an unapproved antibiotic in horses.
Unlicensed antibiotic virginiamycin is the active ingredient of Founderguard, a horse feed additive that has never been though full safety tests or approved for veterinary use in the UK.
Despite this, the Government has allowed vets to import virginiamycin from Australia since 2001, and data obtained by the Soil Association in 2008 shows about 10 tons of Founderguard was being imported annually.
Virginiamycin is closely related to Synercid, an antibiotic kept in reserve for cases of MRSA in humans that fail to respond to vancomycin. This is currently said to be one of the most important antibiotics for treating life-threatening cases of MRSA.
In a statement last year, the Veterinary Medicines Directorate (VMD) said: “There is no robust evidence to suggest that the continued use of virginiamycin will not pose a risk in terms of antimicrobial resistance developing.”
Despite this, the Government said it had no plans to stop the drug being imported before September 2014.
Since 2005, the Soil Association has repeatedly raised concerns over the use of virginiamycin in horse feed. Those concerns were based on the possible transfer of Synercid-resistant strains of MRSA from horses to their riders through direct contact, as horses given virginiamycin were not supposed to enter the food chain.
Revelations over recent weeks about the widespread abuse of the horse passport system, and the discovery of horse meat in the food system, has added urgency to the calls.
Soil Association policy advisor Richard Young said: “Since the transfer of resistant bacteria from horses to humans on food is clearly also possible where horse meat is consumed, we feel that the VMD should revise its timetable and prohibit any future importation of virginiamycin with immediate effect.
“The VMD should make strenuous efforts to ensure that none of the horses that continue to receive virginiamycin in feed while stocks are used up, are permitted to enter the food chain.”