Delivering the City Food Lecture, Melchett said shoppers increasingly interested in quality and taste had found organic affordable.
"This is no longer simply a middle-class market. Over 50% of people in lower-income groups are buying organic food and if they buy direct from farmers, or via box schemes, it needn't be more expensive than non-organic in supermarkets.
"Studies have shown that if shoppers shift away from ready meals and diets high in meat, and buy more healthy, fresh, seasonal produce, and less but better-quality meat, the additional costs are offset."
Major retailers were playing a role in increasing uptake, he said, citing the fact that organic food was a star performer in a record Christmas for Tesco, and that its organic sales had grown 39% in 2006.
"People will make greener choices if they get the right information, opportunity and incentive," he said.
The UK was on the cusp of a revolution in food and farming practices thanks to growing consumer concerns with health and the environment, he added. "It's self-evident that a farming system that's better for our environment is better for our overall health."