Organic food is no healthier than ordinary food, research has found.
A study by the London School of Hygiene and Tropical Medicine concluded there was "no evidence" to support buying organic food for nutritional reasons.
The report, commissioned by the Food Standards Agency (FSA), has sparked controversy because it focused on nutrients and did not compare pesticide levels.
The Soil Association said it was disappointed by the study and called for better research to be carried out.
Policy director David Melchett said: "The review rejected almost all of the existing studies of comparisons between organic and non-organic nutritional differences.
"Also, there is not sufficient research on the long-term effects of pesticides on human health."
However, Gill Fine, FSA director of consumer choice and dietary health, said the study would help people make an "informed choice".
"This study does not mean that people should not eat organic food," she said.
"What it shows is that there is little, if any, nutritional difference between organic and conventionally produced food and that there is no evidence of additional health benefits from eating organic food."
UK sales of organic produce have risen by 22% since 2005, with the market now worth more than £2b.
The FSA's review examined 162 research articles published between January 1958 and February 2008. In total it considered the scientific comparisons between 3,558 organic and other foods.
Research leader Dr Alan Dangour said the report concluded that any differences in nutrition were "unlikely to be of any public health relevance" but conceded that better quality studies were needed.
By Janie Stamford
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