A spike in the cost of tomatoes and broccoli helped bump up the Food Price Index by 2 per cent during July, Statistics New Zealand said.

Tomatoes averaged $13.25 per kg in July, up 34 per cent on the previous month, while the cost of green vegetables rose 14.2 per cent, and accounted for more than half of the rise in food prices during the month.

Fruit and vegetables account for $14 out of every $100 households spend on grocery food.

Statistics NZ's prices manager Chris Pike said the high cost of tomatoes reflected a supply shortage.

Meanwhile broccoli soared 66 per cent during the month.

Lettuce was up 20.7 percent, yoghurt up 14.7 per cent, capsicums up 28.6 per cent and fresh chicken climbed 8.6 per cent.

Lamb prices rose 7.7 per cent and are now at their highest-recorded level.

In the year to July food prices rose 7.9 per cent.

Meanwhile a Statistics New Zealand review has revealed about $38 of every $100 households spend on food, is spent on grocery food.

About $21 was spent on eating out or takeaways, and about $16 was spent on meat, poultry, and fish.

Fruit and vegetables accounted for $14. The remaining $11 was spent on non-alcoholic beverages, such as packaged coffee, soft drinks, and juices.