Privacy International's findings, based on six months of research, placed Google at the bottom of a list of 23 Internet companies examined by the group. Google was the only company to earn the bottom ranking, for "comprehensive consumer surveillance and entrenched hostility to privacy."

Other companies, such as Microsoft and Yahoo, rated slightly better than Google. Microsoft was given a rating of four out of six, for "serious lapses in privacy practices." Yahoo was given a ranking of five of six, one better than Google, for "substantial and comprehensive privacy threats."

"We are aware that the decision to place Google at the bottom of the ranking is likely to be controversial, but throughout our research we have found numerous deficiencies and hostilities in Google's approach to privacy that go well beyond those of other organizations," Privacy International said.

In particular, the group cited the large amount of data that Google collects about its users and lack of privacy controls. "Google's increasing ability to deep-drill into the minutiae of a user's life and lifestyle choices must in our view be coupled with well-defined and mature user controls and an equally mature privacy outlook," Privacy International said. "Neither of these elements has been demonstrated."

Privacy International plans to issue a final report in September. Google executives were not immediately available to comment on the report's findings.

But an open letter to Google CEO Eric Schmidt from Privacy International Director Simon Davies accused the company of engaging in a smear campaign in response to the group's findings. "Two European journalists have independently told us that Google representatives have contacted them with the claim that 'Privacy International has a conflict of interest regarding Microsoft.' I presume this was motivated because Microsoft scored an overall better result than Google in the rankings," Davies wrote.

Google allegedly claimed a conflict of interest exist because one of 70 people on Privacy International's board of advisers is a current Microsoft employee. Davies rejected the charge and listed five critical actions the group has taken against Microsoft, including support for the European Commission's investigation into Microsoft.

"Can I be so bold as to suggest that your company's actions stem from sour grapes that you achieved the lowest ranking amongst the Internet giants?" Davies wrote, demanding an apology from Schmidt.