One New Zealand supermarket is already swinging away from battery eggs and others say they will follow if customers demand it but there may not be enough free-range or organic eggs available.

Five huge UK supermarket chains last week promised to ban or phase out battery eggs. Two more are reducing the shelf space given to the cheaper, less ethically produced eggs and are under pressure to ban them. The turnaround is due to a massive consumer backlash sparked by a campaign by superstar chef Jamie Oliver.

Battery eggs are laid by hens kept in plastic or wire cages, in huge sheds. where artificial lighting means the hens lay an egg almost every day.

Rules introduced in New Zealand two weeks ago mean each hen must have at least 500cm2 of cage space.

The SPCA says overseas research shows by the time they are slaughtered at 18 months old, many battery hens have skin and feather problems and broken bones, due to lack of exercise and the calcium lost through laying so many eggs.

A 2002 Colmar Brunton survey showed 79 per cent of New Zealanders thought battery cages unacceptable, and wanted them banned. In 2006, Parliament's Regulations Review Committee found the rules for battery systems were in breach of the Animal Welfare Act 1999.

But it is unlikely that our supermarkets will ban battery eggs soon there are not enough free-range and organic producers to fill demand. A ban would mean fewer eggs on shelves, and a price hike.

Battery eggs are the cheapest on sale, at about $3.60 per dozen. Barn eggs usually cost about $2 more per dozen, and free-range another $1 on top of that. Organic eggs are selling for more than $11 a dozen at Woolworths' online store.

But Mark Baker, retail sales and performance manager for Foodstuffs which includes New World, Pak'n Save and Four Square expects some of the UK's backlash to trickle down to New Zealand customers.

"Ultimately, if consumers feel strongly enough about the issue, then they will make this known to us and we will listen to ensure we continue to deliver against their expectations."

The egg section at Victoria Park New World, serving the wealthy central Auckland suburbs of Ponsonby and Herne Bay, has already been overhauled. After surveying customers the supermarket pushed its battery hen eggs to the bottom shelves and describes them as caged eggs. Now, free-range and organic eggs make up more than two-thirds of eggs sold. At other Foodstuffs supermarkets, only about one in five eggs sold is free-range, despite increasing consumer distaste for battery farming.

A spokeswoman for Progressive Enterprises, which owns Foodtown and Woolworths supermarkets, said the company was too busy to respond to questions.

An Egg Producers Federation spokesman, who did not want to be named, has not noticed any consumer backlash, although our rules around battery systems are similar to those in the UK, and are in line with International Egg Commission standards.

He says it will be up to individual operators to decide how they respond to market signals, but the issue of price will be important, as eggs are a cheap form of protein.

Top chefs here say free-range and organic eggs taste better and are more ethical. Award-winning Wellington chef Martin Bosley shuns battery eggs and chicken, and want supermarkets do the same.

"I think we've seen a move towards [free range] now. I think people are becoming more and more aware of it ... [Supermarkets] have to bow to the pressure at some stage."

Annabelle White, Sunday magazine's food detective, says free-range and organic eggs are an entirely different experience to battery eggs. "They taste of the earth; there's a lovely sort of distinctive flavour to them."

Source: Stuff Co NZ