There is an acute shortage of organic meat produced in the UK, some of Britain's leading retailers have said.

Tesco's fresh foods director Steve Murrells urged farmers attending the Royal Show at Stoneleigh in Warwickshire to consider organic conversion to lock in premium prices in a growing market.

He pointed to the 11% overall growth in organic sales last year and said that growth in some categories at Tesco was far higher.

Sainsbury's organic meat buyer Matt Johnson said he could easily sell three times as much fresh organic meat if he could get hold of it.

He said the main barrier to growth was the store's policy of buying its beef, lamb, pork and chicken only from British organic producers. "That's our point of difference. We haven't taken the easy way out like Tesco by sourcing organic beef from South America."

He claimed he could build Sainsbury's market share on organic beef beyond its current 40% if he could source more product through processor ABP.

He admitted that a "chronic shortage" of organic pork was making the buy-British policy hard to maintain. "We may have to top up supplies with imports, although it will all have to meet British welfare standards."

At present, Sainsbury sold £5m of bacon and sausages a week, he said, but only 1% of that was organic.

Sainsbury is offering contracts to would-be organic producers to encourage them to undertake the costly conversion, and Johnson said interested farmers should contact Sainsbury's processors. "We are not afraid to have a discussion about prices," he added.

Eastbrook Farms, which sells organic pork under the Helen Browning brand, has found its expansion plans curtailed by a lack of certified producers.

"People are scrabbling for every bit of produce," said MD Tim Finney.