The Epitiro-IDC New Zealand Broadband Index, commissioned by the commission, measures 13 internet service providers (ISPs) every 15 minutes over 24 hours across 11 sites in Auckland, Hamilton, Wellington, Christchurch and Dunedin.
TelstraClear's Cable and DSL services achieved the highest broadband scores in Auckland, Wellington and Christchurch, while Orcon led the market in Hamilton and Dunedin.
Telecom, Vodafone and Slingshot all achieved mid-range to below average outcomes across all five cities in the March quarter report.
Second tier ISPs such as MaxNet, Snap and Compass consistently delivered above average results and took second and third place in their core markets, the report said.
The survey evaluates performance on eight key performance parameters, including synchronisation speed, time-to-connect, and e-mail round trip time. Telecommunications Users Association chief executive Ernie Newman said it was exceptionally difficult for broadband customers to assess the service they were getting, compared to other potential suppliers.
The new regular reports would help considerably in the selection of a broadband service, he said.
"The results show that smaller service providers are leading the way in the technical quality of their service," Mr Newman said.
"This is partly because of their lower customer numbers, although larger providers are perfectly capable of achieving similar ratings if they invest more heavily in the relevant parts of their networks."
Customers unhappy with their service provider would never have a better time to change, he said.
The report found that of the main ISPs, Telecom scored the lowest outcomes in Auckland, Wellington and Christchurch, but was slightly above average in Hamilton and Dunedin.
Hamilton recorded the highest average broadband score across the five main centres -- 16 percent ahead of Auckland and 24 percent higher than fifth-ranked Christchurch.
TelstraClear Cable exceeded the industry average by between 22 percent and 41 percent on key measures affecting speed, time-to-connect and browsing.
The reports also said that TelstraClear's DSL performance was between 6 percent and 14 percent better than the industry average on key metrics, but its DSL performance was highly variable. Its strong results in the three main centres were offset by the lowest outcomes in Hamilton and Dunedin.
Epitiro-IDC said they believed that reflected where TelstraClear had its own cable or DSL network capability and where it resold Telecom services.
The overall results portrayed a market in transition, where recent investment in infrastructure, technology and services had yet to be reflected in the experience of users.
"Those ISPs with the strongest subscriber growth are not necessarily delivering the strongest broadband performance: indeed the results indicate their size and success has led to network congestion, contributing to poorer outcomes than much smaller ISPs focused on a dedicated, technology-savvy market."
Outcomes from investment in the unbundled local loop, high-speed ADSL2+ technology, cabinetisation and new fibre backhaul would begin to take effect over the year, Epitiro-IDC said.
Telecom spokesman Nick Brown said the report itself pointed out that larger providers faced network issues that smaller providers would not face.
"This is to do with having large numbers of customers using the network at any one time," he said.
