Google has collected personal wireless internet data from New Zealand homes through cars sent around the country for its Street View project.

The internet giant confirmed the fact last night, after privacy watchdogs in Germany, Britain and Australia raised concerns about the practice. Fears include the possibility that Google could match people's mobile devices and internet behaviour to home addresses.

An internet safety expert says most people would be surprised how much data Google now holds about them – and the company's word is the only guarantee that it is not misusing the data.

The revelation comes after Privacy Commissioner Marie Shroff joined international counterparts to express concerns to Google about its data and privacy protection.

Australian-based spokeswoman Annie Baxter confirmed Google had collected WiFi information in New Zealand, but refused to answer any other questions. After concerns were raised in Germany, Google global privacy counsel Peter Fleischer said it was "clear with hindsight that greater transparency would have been better".

Information collected included the names and unique numbers associated with residents' wireless networks. The data, which is publicly available, was used to give precise readings of people's locations if they were using Google's mobile map services.

Google "did not collect any information about householders" and could not identify individuals from information collected by its Street View cars, he said.

The Street View project involved cars travelling the streets with 3D cameras to capture panoramic views to go with Google's map service.

Martin Cocker, executive director of internet safety organisation NetSafe, said he was ambivalent about the idea. On one hand, the data was publicly available. "On the other hand, these wireless points – they're ours. We didn't expect they'd be used in this way."

Google's methods were also problematic. "The thing that bugs people is the way Google does these things and tells people about them later."

He believed Google was usually responsible with personal data, but most people would be surprised to learn just how much of it the company held. "We're using Google services so much and, if Google bothered to cross-reference the different things I do, they would know a lot about me."

A spokeswoman for Ms Shroff said she was not aware of Google monitoring WiFi data. Her office would be interested to hear what Google had to say about the practice.

GOOGLE KNOWS

Google is the world's most popular search engine.

It retains users' search histories, along with their internet protocol (IP) address.

Its email service, Gmail, is used by millions of people to store their online correspondence.

Google has trialled targeting advertisements at internet users based on their search history.

Its Street View project built a comprehensive digital database of New Zealand houses and streets.

The company retains personal information that people submit to its iGoogle service.