The privacy commissioner for New South Wales is seeking more information from police about the extent to which data from people's everyday lives is being recorded and stored.

Elizabeth Coombs spoke to Four Corners as part of a report into the Automatic Numberplate Recognition (ANPR) technology - launched by NSW police in 2009 as a means to photograph the number plates of every vehicle they pass on the state's roads.

Tonight's program discusses the practice as part of its program, In Google We Trust, which examines how government agencies and private industry are gleaning data from our everyday activities by following the data trail of an average Australian family.

In it, Ms Coombs says she is eager to clarify the amount of data being taken, how much is stored and whether or not the scheme is in breach of privacy legislations.

"I think it's unlikely that the majority in the community are aware of the potential of that collection and I think many would actually be quite taken by surprise that that is occurring," she said.

"To my mind this issue raises things which are fundamental in the legislation, and that's about transparency and accountability, and the matter that you're raising is one that I most certainly would be speaking further to police about."

NSW Police have been photographing the numberplates of vehicles - regardless of whether they are suspected of any offence - for almost four years and in that time have gathered over 200 million entries.

Three digital cameras are attached to 280 police vehicles and they automatically take the snapshots, time-stamp them before they are added to a vast repository of data which is used as a tool for investigators.

The cars are capable of capturing 1,000 images an hour and thanks to infrared technology, can operate day and night.

The technology is a powerful crime-fighting tool for police, who can scan hundreds of numberplates automatically while freeing them up to look out for other offences.

"It automatically alerts officers to unregistered, uninsured and stolen vehicles, particularly given that as of 1 January this year, registration stickers are no longer required for light vehicles," a NSW Police spokesman told Four Corners in a written statement.

"Once alerted, officers can take the appropriate action against the driver and/or owner of the vehicle and/or confiscating the vehicle."

The statement says no personal information is stored and that there are strict protocols and procedures in place for accessing and retrieving information.

Police can routinely match numberplate registration numbers with a vehicle's owner.

"The information collected by the automatic numberplate recognition units - car photo, registration plate number, police vehicle serial number that captured the read, and where and when the photo was taken -is stored in a separate database for about five years."

Watch In Google We Trust at 8:30pm on ABC1