Google Data Protection Act 'breach'
Google was responsible for a "significant breach" of the Data Protection Act, the Information Commissioner said.
Christopher Graham said the internet giant broke the law when Street View cars collected personal data from unsecured wi-fi networks.
But he said the company will not be fined or face any punishment after it pledged not to do it again.
Mr Graham said Google must delete the data it collected as soon as possible and will face enforcement action if further breaches take place. The company now faces an audit of its paperwork and the measures it has in place to adhere to data protection laws.
Mr Graham said: "It is my view that the collection of this information was not fair or lawful and constitutes a significant breach of the first principle of the Data Protection Act. The most appropriate and proportionate regulatory action in these circumstances is to get written legal assurance from Google that this will not happen again - and to follow this up with an ICO audit."
Peter Fleischer, of Google, said: "We are profoundly sorry for mistakenly collecting payload data in the UK from unencrypted wireless networks. Since we announced our mistake in May, we have co-operated closely with the ICO and worked to improve our internal controls.
"As we have said before, we did not want this data, have never used any of it in our products or services, and have sought to delete it as quickly as possible. We are in the process of confirming that there are no outstanding legal obligations upon us to retain the data, and will then ensure that it is quickly and safely deleted."
Google sparked an international outcry over claims that it has been spying on people with its Street View mapping cars and technology.
The company is accused of unlawfully harvesting data including emails, passwords and website addresses during the creation of the popular product. Last week MPs accused the company of deliberately collecting millions of passwords, websites and emails for commercial gain.
Google has admitted collecting information from unsecured wireless networks as its vehicles roamed residential streets to create the mapping product.