A pro-privacy pressure group has said that it plans to issue a legal challenge in the UK courts to Google over the company’s interception of private data gathered by its Street View vehicles.

Privacy International has taken the action after claiming that an investigation by third party computer forensics experts into how the data interception happened suggested that the interception was deliberate – which would put the internet search company in breach of rules forbidding wire-tapping.

Last month it emerged that cars taking pictures of streets for Google’s Street View service were also collecting snippets of personal data from wireless internet connections in the homes and businesses they were passing.

Google has said this interception was an error and due to rogue code being unwittingly incorporated into the Street View cars. It has agreed to hand over the data to European law enforcement bodies, and is carrying out an internal review to discover who created the rogue code which enabled the data to be collected, and whether any action should be taken against the individual concerned.

However, Privacy International said the third party report showed that the code had been deliberately set to store private data, which is a violation of the UK’s Regulation of Investigatory Powers Act (RIPA).

“The independent audit of the Google system shows that the system … intentionally separated out unencrypted content of communications and systematically wrote this data to hard drives. This is equivalent to placing a hard tap and a digital recorder onto a phone wire without consent or authorisation,” the pressure group said.

Eric Schmidt, Google’s chief executive, said last week that the data collected could contain parts of private e-mails, and personal information such as bank account details, and he publicly admitted: “We screwed up.”

But Simon Davies of Privacy International told the Financial Times in London. “Why they did this is irrelevant to the prosecution going ahead.

“There is a constant sense of Google saying they didn’t mean any harm.

“But if Google gets away with it, what will stop someone else from doing it in six months’ time?”

Data protection authorities in Hamburg are also considering whether there are grounds for a criminal prosecution over the interception.

Privacy International’s complaint is likely to be filed by early next week.