Consumers can be very fickle and stubbornly refuse to change their minds once they have formed an opinion about something.

Eggs are a good example, where sales plummeted in the wake of the food scare started by former health minister Edwina Currie in 1988 when she claimed that most were infected with salmonella bacteria. Consumers boycotted them despite the risk of an egg being infected with salmonella to be less than 200 million to one. That led to massive losses and four million hens being slaughtered as well as the destruction of 400 million eggs. The government was forced to offer a compensation package of millions of pounds to cover the cost of purchasing surplus eggs and for the slaughter of unwanted hens.

A raft of measures were introduced into the poultry industry including movement restrictions, compulsory slaughter and disinfection procedures, as well as a voluntary, industry-led vaccination programme that began in breeding flocks in 1994 and in laying flocks in 1998.

Those measures have led to a dramatic fall in the number of cases since the late 1990s. Legislation requiring compulsory slaughter of poultry infected with salmonella has now been revoked, but the mass vaccination of poultry has continued by those breeders subscribing to the Lion Quality Code of Practice and using the Lion Mark on eggs.

Sadly, until recently many folk have continued avoiding eggs due to past safety advice about the need to cook them thoroughly. That all changed about a year ago when official advice from the Food Standards Agency encouraged everyone - including "vulnerable groups" like mums-to-be, young children, and the elderly - to enjoy runny eggs, provided they are produced to British Lion standards. Since then retail egg sales have soared to new heights, with official figures showing egg sales volume up 5 per cent.

Egg sales may be booming once again, but the demand is only for brown ones. In the 50s and 60s, white eggs were all you could find in British shops, as the breeds that produce them are more efficient at converting feed into eggs. Sadly, over the years fickle British consumers have decided they prefer brown ones - probably wrongly associating them with free-range eggs, or perceiving them to be somehow more nutritious. The end result is that you never see white eggs for sale in British supermarkets.

Contrast that absurdity with the US where the most common type of hybrid hens used in large-scale egg production lay white eggs that are just as tasty and nutritious as brown eggs.

Free-range eggs account for 53 per cent of UK packers' throughput, but it's been a bleak year for free-range egg producers with soaring supplies putting prices under pressure. Now they are having to address another fad and ask consumers to eat a range of egg sizes rather than always reaching for a box of large ones. The British Free Range Egg Producers Association (BFREPA) has launched a campaign to show consumers that hens naturally lay a range of sizes and is asking them to align their shopping habits with what hens do naturally.

About 13 billion eggs are eaten in Britain every year and the BREPA says shoppers prefer to buy large or very large eggs rather than medium or mixed weight boxes. The resulting supply imbalance is exacerbated in years such as this when hot weather leads to hens eating less food, causing them to lay eggs which are graded as medium sized.

James Baxter, a free-range egg farmer and chairman of BFREPA reckons a change in buying habits would be better for hens and farmers and said: "Hens naturally lay smaller eggs when they are younger and the size increases as birds get bigger.

"Every day half the eggs laid by British free-range hens are classed as large or very large, which means that half are medium or small. But consumer preference means medium eggs - which are just as nutritious and tasty - are worth less at the farm gate and more will be sent for processing rather than sold as a fresh shell egg.

"We would love to see more consumers buying medium or mixed weight boxes of eggs which contain medium and large eggs. It support what hens lay naturally."

BFREPA's campaign began with the launch of a video on Facebook featuring free-range egg farmer Susie Macmillan and her 18,000 organic free range hens. She explains the main difference between a medium and a large egg is not the size of the yolk - where the bulk of the nutritional value is contained - but simply a greater quantity of white.