The Deputy Data Protection Commissioner has said that Google's retention of Street View data in violation of agreements made with European governments is "clearly unacceptable."
The company angered regulators in 2010 when it acknowledged that its mapping cars had captured passwords and other data transmitted over unsecured wireless networks.
The Street View cars were supposed to be capturing photographs of streets only, but subsequent investigations revealed that it intercepted data including legal, medical and pornographic material.
The California-based company, which has its international offices in Dublin, had promised to delete the data, but it acknowledged today it had retained some of it.
Gary Davis said his organisation had conveyed its "deep unhappiness" to Google and wants answers by Wednesday.
Google said that other countries affected included France, Belgium, the Netherlands, Norway, Sweden, Finland, Switzerland, Austria and Australia.
In a letter published by Britain’s Information Commissioner’s Office, Google apologised and said it discovered the data while undertaking a manual review of Street View disks.
It said it had contacted regulators in all of the countries where it had promised to delete data but realised it had not.
The disclosure comes just over a month after Britain’s ICO reopened its investigation into Google's Street View, saying that an inquiry by authorities in the United States raised new doubts about the disputed program.
In April, the US Federal Communications Commission fined Google, saying the company "deliberately impeded and delayed" its investigation into Street View.