A report by Consumer magazine says using a hands-free phone while driving is just as distracting as using a hand-held phone
New road rules which took effect on 1 November ban the use of hand-held cellphones while driving, so hands-free devices are now encouraged.
Consumer magazine trialled four hands-free devices when trying to find the best way to make and receive calls when driving - a wired earpiece, Bluetooth headsets, Bluetooth speakerphones and a phone cradle.
Its test found holding a conversation on any of the hands-free kits was distracting - especially when dialling a number while driving.
"It took our attention away from navigating intersections, parking, changing lanes - not to mention cyclists, pedestrians, and other cars doing strange things," the magazine said.
"Using a hands-free phone wasn't any different from using a hand-held one."
The wired earpiece was the easiest to use, but voices sounded muffled, while the Bluetooth headsets didn't feel stable against the ear and voices sounded muffled and faint, the magazine said.
Bluetooth speakerphones didn't respond very well to New Zealand accents when attempting to voice-dial, and had distorted sound.
The magazine said it was sensible to pull over and stop before making a call - even with voice-recognition dialling and a hands-free phone.
What do you need to know about the mobile phone ban? Read more here.