Mr Guthrie said the cost of phasing out battery cages in that time would also be prohibitive.

The egg industry says that will allow it to meet the conditions for phasing out battery cages.

The industry is phasing out battery cage eggs by 2022, but new controversial colony battery cages, which are slightly larger, will be allowed.

Battery cages have been outlawed in the European Union and some US states, while New Zealand is phasing out battery cages over the next decade.