Telecom is being advised to pay compensation to companies caught in an internet outage in Wellington on Wednesday.
The fault occurred about 2pm and lasted about three hours. It also affected other regions.
Telecom says the problem was with some ethernet sites that service corporate customers. It is still trying to isolate the cause.
The Telecommunications Users' Association says such faults have happened too many times and a company like Telecom should not have them.
He says the company can't duck the question of compensation because of direct and indirect costs to those affected.
NZX says stock markets would have completely closed, were it not for its own backup systems.