A supermarket giant says crime has surged in its North Island stores.

Foodstuffs recorded 3900 separate incidents from the start of May to the end of July, a 59 percent year-on-year increase.

Serious incidents including assault, robbery and burglary have more than doubled in the past year and are up 13 percent on the last quarter.

Foodstuffs North Island CEO Chris Quin says the biggest issue is organised theft, with people stealing products to make money.

"Secondly, it's sadly people with addictions, and they're trying to support that addiction through theft. And then our social media driver, where people are trying to make a hero of themselves by doing some of this stuff."

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