The software, which has not yet been launched in the UK, is an add-on to Google Maps and Google Earth that offers photographs of streets and cities. However many of the photographs feature passers-by who have been caught unawares.
According to UK privacy group Privacy International, the software breaks UK data protection laws because those pictured in the photographs haven't given consent.
"In our view they need a person's consent if they make use of a person's face for commercial ends," said Privacy International's Simon Davies.
In the US, Google has started trialling technology that blurs the faces of passers-by but Privacy International has voiced a number of concerns over this and has written to the software giant asking for a breakdown of the technology and the steps, if any, that Google takes to consult the public over the use of their images.
If Google doesn't respond to Davies' letter, he intends to ask the Information Commissioner to suspend the service in the UK.
"We've spoken to Google in the past about this and received a snide response telling us to look more closely at their blogs. We've been told by engineers at Google that the technology is not ready to be deployed," he said.
Google maintains it complies with all local laws.