It's the largest increase in food costs for more than three years

Stats NZ says food costs are up by 4.1 per cent in the year ending June 2020.

Fruit and vegetable costs increased by 10 per cent - largely because of rising tomato prices.

Consumer Prices Manager Sarah Johnson says it's because they're out of season.

She says many growers have also changed the way they heat their greenhouses, because of carbon emission prices.

Ms Johnson says this affects the supply of tomatoes - and in turn the prices.