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The Grampian Country Food Group, which supplies 200m broilers a year, is stopping the use of growth-promoting drugs in response to consumer demands for healthier eating.

The move follows concern that the overuse of antibiotics poses a threat to human health by helping to create so-called microscopic "superbugs" which are resistant to modern medicines.

The decision could have a substantial impact across a farming industry which has previously claimed that antibiotics help to improve the quality and efficiency of production while also keeping businesses viable.

'No deterioration in quality'

Director of the Grampian Country Food Group Malcolm Smith: "This is what the customers want"

Two of Grampian's biggest customers, Marks & Spencer and Tesco, welcomed the move.

M&S spokeswoman Sue Sadler said: "This is an important development. It is something we have been looking at for some time and we are pleased that Grampian have announced this step forward of their own accord."

Antibiotics are used extensivly in intensive pig-rearing

She added M&S would now expect other meat producers to look at the possibilities of stopping the use of antibiotics to speed growth.

Supermarket giant Asda has also asked its producers to conduct trials into a drug-free approach to rearing chickens.

Grampian, which supplies nearly a third of all home-grown chickens in the UK, made the announcement after an antibiotic-free trial involving up to 1.5m birds showed no deterioration in their quality or welfare.

Malcolm Smith, chief executive of the firm's chicken division, said: "We have conducted exhaustive field trials with focus groups who have all said they would like us to remove growth promoters from the food chain."

He said the Aberdeen-based company did not intend to charge a premium for its antibiotic-free birds.

Investment in rearing birds with improved heating and ventilation along with good quality feed had reduced the stress on birds, making it possible to remove the antibiotics, according to Grampian.

Health concerns

Food safety experts at Friends of the Earth welcomed the decision.

Some bugs are developing resistance to antibiotics

Adrian Bebb, food campaigner for FoE, said: "It is quite clear that there is a huge problem with resistance building up in the human population and it is partly because of unnecessary use of antibiotics in farming."

Growth promoters have been used extensively in animals' feed and water in British farming for 40 years, especially in the pig and poultry industries.

Ben Gill of the National Farmers Union told BBC radio: "There is nothing to suggest that any effects in the meat are causing any problems with human health. It is more regulated now than ever before."

But he said the industry did want to trim its dependency on antibiotics.

"We want to reduce our input costs. This is one way we can do it, if it's sustainable," he said.