"Antibiotics are still being used to force pigs to grow unnaturally quickly, despite a ban and amid fears about the impact on human health," the UK organic lobby group Soil Association said on Monday.
It has been illegal for EU farmers to use certain antibiotics to make pigs grow faster since 1999. But sales of the growth-enhancing drugs have soared in recent years, the group said.
EU health ministers pushed through the restrictions on their sale because of concerns they could reduce human resistance to similar drugs.
"The Soil Association is concerned that some pig farmers are using a loop-hole to continue feeding these drugs to their animals - although the drugs cannot be legally used to promote growth, they can be prescribed by vets to prevent diseases in healthy animals," it said in a statement.
"We suspect that they are secretly being used for growth promotion," the group added.
Hooked on antibiotics
Soil Association policy advisor Richard Young said the drugs prescribed were already starting to lose their effectiveness against preventing disease because of overuse.
"It is inevitable that animals become ill when they are kept in crowded conditions, which is why the intensive pig industry is still hooked on antibiotics," Young added.
"We suspect [the drugs] are secretly being used for growth promotion"
The Soil Association
The Soil Association said widespread use of the drug Tylosin, a member of antibiotic group "macrolides" and banned as a growth promoter, was a particular concern.
Government figures show that the amount of macrolides prescribed by British vets jumped from 23 tonnes in 1995 to 55 tonnes in 2001, but a breakdown for Tylosin use has never been published.
Tylosin can still be used for therapeutic use under EU rules.
The Soil Association said the government must act to ensure that the drug is not being inappropriately used and is demanding it set up an expert panel to monitor the industry's use of such drugs.
"The situation makes a mockery of the growth promoter ban, which was brought in because of concerns from scientists, despite strong industry opposition," Young said.
British pig farmers use four times as many antibiotics than their Danish counterparts and the meat produced contains more antibiotics per tonne of meat produced than any other EU member state, official studies have shown.
EU countries are still phasing out the use of antibiotics for promoting growth in animals, with a 2006 deadline set for complete abolition.
The drugs have been used for decades to prevent disease and increase weight gain in animals, shortening the time between breeding and slaughter.