A new report suggests there are problems enforcing the use of security cameras in taxis, and that penalties for breaching the rules need to be tougher.
Since August 2011 taxis in major towns and cities have had to be fitted with interior security cameras and communications systems.
Taxi companies are required to ensure their cameras are working and have inspections at least every six months.
But a review of taxi driver safety by Opus International says the new requirements are not easy to enforce.
Since the law was introduced assaults on taxi drivers have actually gone up, but officials suggest this may be because drivers are more likely to report an attack because they have footage of it.
Taxi Federation spokesperson Roger Heale said the cameras have been effective with a 40 percent decrease in serious assaults, as well as improvements in driver safety, particularly at night.
But he concedes there are problems.
"There are some operators within each fleet, generally speaking, that are running around with cameras that are not working. And that represents an issue potentially for the driver and also for the passenger."
Associate transport minister Michael Woodhouse said he believes the level of compliance is high but says the Federation has raised its concerns with him and he's considering it as part of the review in to how effective the cameras have been.
"My strong preference is for self-regulation, because after all it's their members and their employees that have the most to gain from the safety benefits of cameras.
"And I certainly haven't ruled out more compliance - if it's a wide-spread practice that taxi companies are not complying with the present rules, sure I would consider it. But at the moment that's not the goal."
But Mr Woodhouse said he has also warned the Taxi Federation that any increased compliance costs will have to be met by the industry.
The review is expected to be completed later this year.