The company admitted downloading personal data from wireless networks when its fleet of vehicles drove down residential roads taking photographs for its controversial Street View project.
Millions of internet users have potentially been affected.
One privacy campaigner described the intrusion as “absolutely scandalous” and called on Google to launch a full inquiry into the affair, reports the Telegraph.
The Information Commissioner’s Office (ICO), the privacy watchdog, said it would be looking into Google’s admission.
Images for Street View were gathered by vehicle-mounted panoramic cameras starting in 2008.
In May this year, Google confessed the vehicles had also been gathering information about the location of wireless networks, the devices which connect computers to the telecommunications network via radio waves.
Now the California-based company has revealed that far more information was harvested than was previously thought, after privacy regulators in seven countries analysed the data.
”It’s clear from those inspections that while most of the data is fragmentary, in some instances entire emails and URLs [web addresses] were captured, as well as passwords,” said Alan Eustace, Google’s vice president of engineering and research.
”We want to delete this data as soon as possible, and I would like to apologise again for the fact that we collected it in the first place.”
The company archived all the material it had gathered, which included emails being sent by private individuals, the web pages they were viewing and passwords they may have entered as the Street View vehicle passed their homes.
It is believed that only wireless networks that were not password-protected were affected.
Simon Davies, director of Privacy International, said: “It’s absolutely scandalous that this situation has developed and so many people have had their communications intercepted.”
A Google spokesman said the wireless data was gathered so the company could amass details of Wi-Fi hot spots that could help provide location-based web services.