On 25 November, bakers across the country will put on their aprons to carry out a British tradition dating back to the Victorian era, when families would gather together to make their festive pudding.

But this year farmers are calling on consumers to quit their obsession with using large eggs in the recipe and instead buy a box of mixed weight to support what hens lay naturally; a range of egg sizes.

James Baxter, a free range egg producer and chairman of the British Free Range Egg Producers Association (BFREPA), said: "British consumers have a love affair with large eggs and we don’t really know why.

"It’s a relatively new phenomenon which is probably driven by a perceived sense of value and modern recipes insisting on large eggs when traditionally size wasn’t specified.

"We want consumers to understand that hens lay a range of sizes – from small to large – and we would love to see shoppers choosing mixed weight or medium eggs which are just as nutritious and tasty."

Only half the eggs an average hen lays in its lifetime will be large, with the rest being medium or small.

Eggs are graded by weight and the increase in size is more attributable to the quantity of white rather than the amount of yolk where the lion’s share of nutrition is found.

BFREPA says bakers should follow the Womens’ Institute – a global authority on baking – which has many Christmas pudding recipes using medium eggs or where size is not stipulated.

About 13 billion eggs are eaten in Britain every year and BFREPA says shoppers prefer to buy large or very large eggs rather than medium or mixed weight boxes, and too often recipes are misleading when they state the size of the egg needs to be large.

Mr Baxter said: "We want to consumers to know that bigger is not always better.

"In the run-up to Christmas, we would love to see more consumers buying medium or mixed weight boxes of eggs which contain medium and large eggs – it’s better for the hens and supports what they lay naturally."

BFREPA launched its campaign in October with a video 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.

More than 85k people have watched the video on Facebook with dozens pledging to make the change to medium or mixed weight boxes.

You can watch the Facebook video here.