The Privacy Commissioner's Office is worried about the expanding use of Facial Recognition Technology in supermarkets.

Foodstuffs is using the technology in more than 30 stores across the North Island.

Retail NZ has been backing the move, saying it should be a tool used to stop crime.

But there are also long held concerns about privacy and what happens to the biometric data.

Deputy Privacy Commissioner Liz MacPherson spoke to Charlotte Cook.