MikeAqua:In NZ our vehicles are rated to suit the Aussie regs. So a Pajero and an ASX have the same unbraked tow-weight rating.
I thought the NZ limit was based on stopping from x km/h in y metres rather than absolute weights. Most vehicles would have the same ability to absorb additional weight, it's when the trailer is also braked that the ability of the vehicle to control the trailer comes in. Then the Pajero can tow 2-3 times ASX weight depending on model and towbar.
Ignoring the manufacturer specified limit would probably count towards the careless driving charge following the prang.