A US judge has ruled that Google did break the law when it harvested unsecured WiFi data while collecting images for its Street View mapping service, upholding an earlier ruling by a federal court.

The decision means that a group of users who claim their privacy was violated by Google can now press ahead with their claim for damages against the search giant.

Google had hoped to have the case dismissed, arguing that its ‘mistaken collection’ of the data – which includes personal emails, user names, passwords, videos and documents – did not break wire-tapping laws because data transmitted over Wi-Fi is a ‘radio communication’ which is ‘readily accessible to the public’.

However, Circuit judge Jay Bybee disagreed, stating: “Even if it is commonplace for members of the general public to connect to a neighbour’s unencrypted wi-fi network, members of the public do not typically mistakenly intercept, store, and decode data transmitted by other devices on the network.”

A Google spokesman said that the company was disappointed with the decision and is considering its next steps.

John Simpson of Consumer Watchdog said the decision was a “tremendous victory for privacy rights”.

“It means Google can’t suck up private communications from people’s Wi-Fi networks and claim their ‘Wi-Spying’ was exempt from federal wiretap laws,” he said. “Because Google’s “Wi-Spy” activity was so extensive, the potential damages could amount to billions of dollars.”

Meanwhile, Marc Rotenberg of the Electronic Privacy Information Center described it as ‘a landmark decision for internet privacy.’

“Users should be protected when a company tries to capture data that travels between their laptop and their printer in their home,” he said.

Earlier this year, Google escaped a fine for harvesting personal data from home and business Wi-Fi networks in the UK, after the Information Commissioner’s Office (ICO) decided that Google had not caused enough harm to warrant a fine of up to £500,000.

However, the Federal Communications Commission in the United States issued Google with a $7m penalty for the privacy breach – the largest ever – and a further $25,000 for obstructing its investigation by refusing to identify employees involved in the project or produce internal documents.