Somerfield's move to source nearly half its free-range eggs from France is a sure sign of a UK supply crisis, producers say. The retailer is not the only one looking at sourcing abroad, but producers here say they warned customers of the impending shortage a year ago. And it all comes down to price.

Egg major Deans says its producers would lay down another 400,000 poults, capable of laying up to 150 million eggs a year, but can't justify the investment. An increase of just 5p/dozen would make all the difference, said operations manager Andy Joret. "All that is holding them back are low prices and lack of confidence. These farmers could be up and running in six months."

If the industry increased laying hen numbers by as little as 500,000, it would transform the supply situation, he added.

Prices must rise or retailers must take the responsibility for a deepening shortage of British free-range eggs, said John Widdowson of the British Free Range Egg Producers' Association.

His organisation warned retailers of the problem a year ago and wrote to all of the big four in March, but only received a single letter back - from Sainsbury's. "It had zero effect, and now, as we warned, we are short of eggs. If we get the price rise we want I have no doubt we will be able to meet demand. We have never failed to do so in the past."

Prices fell last spring, when free-range eggs were discounted below the cost of battery eggs in a retail price war. Since then, the cost of a dozen medium free-range eggs at Asda has risen 7p to £1.55.

But it costs about 65p to produce a dozen free-range eggs, with farmers receiving almost exactly that from the packers. With expansion costing about £250,000 per 12,000-bird flock, excluding land, there was not the confidence to expand, he said.