FREE range eggs are no longer on sale in shops after the largest ever outbreak of bird flu has forced farmers to keep hens inside.

Producers are now only allowed to sell eggs labelled as barn eggs because the birds are no longer allowed to range outside and have had to be kept inside to protect them from bird flu.

Although the numbers of bird flu cases are dropping, there are currently two cases in the North East and none reported in North Yorkshire, the industry has been forced to change labelling because chickens have been kept indoors for more than 16 weeks.

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So far this year there have been 86 cases, the highest number recorded, last year there were 26 cases. North Yorkshire was badly hit in the first two months of the year with outbreaks near Leeming Bar, Thirsk and Richmond. Over 65 per cent of egg sales in the UK are now free range.

Aimee Mahony, chief poultry adviser at the National Farmers' Union said the government's advice was that there was "still a high level of risk" to birds of catching flu.

"This is an incredibly difficult time for all bird owners and vigilance remains vital. Farmers are following ‘stringent biosecurity measures’ and adapting hen houses to make birds more comfortable,” she added.

All keepers of birds from huge breeders to people with just a few in a back garden are told they must continue to keep them undercover.

The British Egg Industry Council which represents many egg producers said they fully support the Government’s decision to keep hens safe.

Mark Williams, Chief Executive of the British Egg Industry Council, said: “Free range farmers love to see their hens enjoying the outdoors and exploring the range. However, we need to ensure that it’s safe before they venture outside and hopefully it will only be a very short period before they can do so again.”

"As free range birds have now been inside for some time, there will be some changes to packs required by legislation. As these are free range hens temporarily housed for their welfare, producers will continue to use free range packs, however, each pack will be marked with the words ‘Barn eggs’. In addition, each egg will be marked with a number 2 to signify that it is a barn egg, for example 2UK54321, which is explained on each pack.

“Retailers will also be communicating with customers to explain the changes.

“We undertook research that showed consumers want to support free range hens and free range farmers. Marking free range packs and eggs temporarily as Barn is not only the most practical solution, but it also means consumers can continue to buy eggs from free range hens, albeit temporarily housed, while farmers can ensure the hens are safe and well.”

The UK Health Security Agency says avian influenza is primarily a disease of birds and the risk to the general public’s health is very low.