Retail sales of free-range eggs rose by almost 20% in volume and 46% in value in the first four weeks of 2008, with four in every 10 eggs sold at retail now free-range.

According to TNS data issued by British Lion eggs, free-range now accounts for more than half the retail market value. Total egg sales were up more than 1% in volume, following growth of 2.5% in 2007, and market value rose by a third to £56m.

Andrew Parker, chairman of the British Egg Industry Council, said: "We put the sustained growth down to the wealth of scientific evidence showing eggs are good for you, as well as new research that shows that eggs can help you slim."