The Information Commissioner's Office served Google Inc. with an enforcement notice, giving it 35 days to kill material captured in the project that featured camera-toting vehicles shooting images of the world's streets.
To make sense of the pictures, Google had to be able to place precisely where the properties being photographed were located. Using a computer program, the vehicles taking the images used local Wi-Fi outlets to place the properties, and in doing so, collected snippets of data from the Wi-Fi networks.
The disclosure angered Internet users when it was first revealed in 2010, and Britain was one of several countries that launched inquiries. But it accepted Google's explanation that it had destroyed the material.
But last year, Google acknowledged that a handful of the discs had been discovered and the regulator promptly re-opened the investigation. U.S. authorities raised concerns about the engineer who created the software.
However, investigators in Britain concluded there wasn't enough evidence on a corporate level to prove that Google had intended to collect personal data, and stopped short of imposing a penalty. In the United States, it paid a $7 million fine to settle a multistate investigation.
"The early days of Google Street View should be seen as an example of what can go wrong if technology companies fail to understand how their products are using personal information," Stephen Eckersley, the office's head of enforcement said in a statement.
The data regulator said the breach would have been worse had the data been disseminated. Google has insisted it was never examined.
Google promised to comply with the order.
"We work hard to get privacy right at Google," the company said in a statement. "But in this case we didn't, which is why we quickly tightened up our systems to address the issue. The project leaders never wanted this data, and didn't use it or even look at it."
The enforcement notice adds to the growing unease in Europe about whether Google was taking privacy concerns too lightly. France on Thursday gave the Internet search engine three months to be more upfront about the data it collects from users or be fined. Other European data watchdogs are also concerned.