Shoppers buying free-range eggs are being warned that they may not strictly be from free-range chickens while the threat of bird flu hangs over the industry.

Many egg suppliers that have the ability to do so have put their hens into lockdown, restricting their roaming, as a precaution to protect them from bird flu, which has been discovered in a native bird in Wairarapa.

Australia is facing a wider outbreak. It was reported this week that the country had had its first mass mortality event in a group of native seabirds in South Australia.

There, the Australian Competition and Consumer Commission has paused enforcement measures for free-range egg labelling, to allow free-range producers to keep hens inside to protect them from disease.

The Commerce Commission said it would take a similar approach in New Zealand.

Simon Pope, head of fair trading and product safety investigations, said it recognised the current difficulties faced by the industry and sympathised with those who were affected.

"The Fair Trading Act does not allow us to give exemptions to egg and poultry producers in relation to free-range claims, even when there is an outbreak.

"However, we can exercise discretion in deciding whether to investigate or take enforcement action. We would consider all relevant circumstances in a situation where such a decision was required.

"The Commission has produced guidance for egg and poultry meat producers related to how we exercise this discretion."

It said it would expect producers and retailers to consider things like a public awareness campaign so shoppers understood why birds might not be free-ranging for health reasons. They could also use temporary packaging or add stickers on the free-range labels.