The Office of the Privacy Commissioner wants to know how bars cracking down on underage drinkers and troublemakers intend to keep the personal information they collect secure.
Some bars are forcing people to have their pictures taken and their IDs scanned to keep troublemakers and underage drinkers out of their premises.
But the Privacy Commissioner wants to know how they are making sure personal information cannot be reused for anything else.
The Trinity Group, which operates 18 restaurants throughout the country, is trialling the system but says it would need to consider the legal ramifications of holding such information before it's rolled out.
Managing director Jeremy Smith says the information collected during the trial will be deleted once it is over.
Two bars in Auckland and a pub chain in Wellington are using scanner machines that store pictures and information from people's IDs so they can catch people using fake IDs.
Bars can also share information about patrons who have been kicked out of their premises.
Supplier Thomas Rawson says people can be assured their private information is not being looked at because the data is encrypted.
He says the system authorises only the venue manager to access the information, and there is a data log of everyone who uses the computer.
Mr Rawson says it is up to bar staff to use their discretion to refuse entry to a person who doesn't want to have their ID scanned or their picture taken.
Photos and drivers' licences can be deleted from the system on request after the person leaves left the bar.
The owner of Prospect of Howick bar, Barry O'Shaughnessy, says there have been no complaints from patrons since his bar started using the machines more than a month ago.