The egg industry is in a flap over a new animal welfare code for layer hens, which has taken it by surprise.
The new code, which Primary Industries Minister David Carter released on Thursday, calls for battery cages for egg production to be phased out within 10 years and replaced with larger colony cages or with alternative barn and free range systems.
More than 80% of the eggs produced in New Zealand are laid in battery cages.
The Egg Producers Federation says it supports the move to colony cages which would increase the minimum space for each hen from 550 to 750 square centimetres.
But chairman Michael Guthrie said it's been gob-smacked by the shortness of the phase-out period which he says would be physically impossible to achieve.
He says although the headline for phasing out battery cages is 10 years, the fine print suggests it is more like four years, and definitely six.
"Even if you were going to free range from cage or barn, there's no physical way that you can do this in four years, where 50% on that date would have to be there."
Mr Guthrie said the cost of phasing out battery cages in that time would also be prohibitive.
He says it will force some egg producers out of the industry, egg prices will increase and production will fall.
Mr Guthrie said a conservative estimate of the cost of moving all the egg producers who are using cages to egg colony production is $150 million, but it would be about $250 million if they changed to free range production.
"Some of these small farms owned by families, where are they going to get $3 million? There are only 42 producers, so that's a huge burden you are going to put on a very small group, it's impossible."
Mr Guthrie said the Egg Producers Federation is now considering legal action against the new welfare code.
Green Party says ban all hen cages
Animal welfare advocates say the new code doesn't go far enough because it still allows hens to be kept in cages.
The Green Party says the larger colony cages do not meet the fundamental purpose of the Animal Welfare Act, either.
Spokesperson Mojo Mathers said the code entrenches the use of loopholes to allow factory farms to continue to keep animals in cruel conditions.