Sales rose 30 per cent to 1.6 billion during 2005, according to the Soil Association's annual report, with two-thirds of consumers knowingly buying pesticide-free food. But the fashion for "going organic" means retailers may have to increase imports to meet demand, it warned.
The bulk of organic produce is bought in supermarkets, which
stepped up their UK sourcing by 13 per cent, so two-thirds of organic produce on their shelves is now from the UK - excluding items such as citrus fruits which are grown only overseas.
Helen Browning, of the Soil Association, said: "In some ways, it has been good news, because producers are getting a sensible price for their products. But the downside is that availability will be difficult to maintain.
"There is a danger retailers will be forced to look abroad for supplies and consumers might be frustrated over time at not being able to purchase the range that they want."
Organic UK pork, beef and cereals are already in short supply.
James Withers, the deputy chief executive of NFU Scotland, said switching to organic was no dream ticket for farmers. "As prices fall, so do the margins. So any benefit to converting might be cancelled out," he said.