Britain's farm ministry estimated earlier this year that domestic production accounts for 44 percent of all organic food sales and 62 percent for foods that can be grown in the UK.

"There is not enough organic food on the shelf to keep pace with demand. Our hunch is that the market is now constrained by availability," Browning told Reuters on Wednesday.

Retail sales or organic products in the UK were worth about 1.6 billion pounds (US$3.02 billion) during 2005, an increase of 30 percent on the previous year, according to figures released by the Soil Association.

Browning said sales would have grown by 30 percent again this year but for the supply constraints.

Analyst Datamonitor earlier this month forecast the UK market for organic products would rise to nearly 2.7 million pounds by 2010, up almost 69 percent from the 2005 level.

Browning highlighted pork and beef as two products that are "massively undersupplied," adding that it takes two to five years for a farmer to convert to organic production.

The shortage is less severe in poultry where it is possible to convert to organic production much faster, she added.

FARMER OPPORTUNITIES

"It is our aim to source 100 percent British organic meat and we believe there is a huge opportunity for more British farmers to benefit from growth in this year," a spokeswoman for Britain's leading supermarket chain Tesco said.

The Tesco spokeswoman said the retailer had held organic conversion seminars during the summer to encourage more British farmers to consider organic farming.

British farmers are, however, wary with many dairy farmers converting to organic operations in the late 1990s only for a supply glut to mean many had to sell their milk into the conventional, lower priced, market.

"A lot of dairy farmers went through a very difficult time," Anthony Gibson, communications director for Britain's National Farmers' Union said.

"There obviously are opportunities and it will be the right thing for some farmers to do but we don't want to see a mad rush as happened in the past. It is a small section (of the UK food market) and it is very easily oversupplied," he said.

The rise in imports of organic products has also sparked environmental concerns which may help slow the growth in demand.

A survey of British organic shoppers published by the Soil Association earlier this year showed more than 80 percent would rather purchase locally grown non-organic products that imported organic items.

Reasons given included supporting local producers and reducing food miles, a term used to highlight the damage to the environment of transporting food over long distances.

"The environment aware consumer should go for the locally produced product every time. Importing food half way across the world has an adverse effect on climate change and the viability of the rural economy," the NFU's Gibson said.

Browning said the environmental issue had sparked a lot of debate but questioned the wisdom of relying on non-organic crops which had, for instance, been heavily sprayed with pesticides.