People are being asked to buy small and medium eggs - rather than oversized eggs - in a bid to improve hens' welfare.

The Devon-based British Hen Welfare Trust (BHWT) say that prolapses are not uncommon in birds laying large and extra-large eggs.

It's bad news for farmers, too, as they are paid less for smaller eggs.

Founder of the BHWT, Jane Howorth MBE, said: "Size matters, at least when it comes to eggs.

"Consumers may be aware of what being free range means to a hen, but now is the time to give consumers the power to help hens further by simply switching their thinking on egg size.

"Over half the eggs laid by commercial laying farms are large or extra-large and these whoppers cause birds increasing welfare issues with prolapsing not uncommon.

"Mixed weight eggs are currently sold by a handful of supermarkets, but generally shopping habits remain stuck in the outdated ‘big is best’ mindset.

"Everyone’s a winner if we simply change our thinking.

"Small or mixed weight eggs provide consumers with a bigger yolk to white ratio - surely most of us agree the yolk is the best bit? - farmers get a fairer price for each egg laid regardless of size and most of all it takes the pressure of our hardworking hens and allows them to do what comes naturally without interference from genetic modification.”

She says that hen welfare is being compromised and this is leading to health problems for hens that lay large eggs.

Jane recently gave a talk to influential food writers and chefs in which she encouraged them to switch their thinking on size when writing recipes.

She pointed out that more than 42 per cent of eggs are large or extra-large.

Mediums and small eggs are downgraded for use in the processed food sector, meaning the yolks are not best utilised and the farmer loses out financially as they have less value.

Hen keepers know that their flocks squawk after laying an egg and report that the larger the egg, the louder the noise.

Jane said: "Please buy small, medium or mixed weight eggs to help hens – you’ll get more yolk for your money if you do, and the farmers and the hens will thank you.”