Bert Borger says there's is a lack of understanding about pig-farming methods, which range from indoor sow crates, to free-farming - where the animals are raised in larger eco-barns - through to free-range where the pigs roam outside all year round.

According to Radio New Zealand, he says current labelling is unclear on whether pork is from New Zealand or imported, and how it is farmed.

Mr Borger says the pork industry needs to set standards on what free range actually means, which countries such as Australia already have.

Mr Borger farms heritage Tamworth pigs on a 400-acre farm at Paparoa on the North Kaipara Harbour.