A group of US congressmen has asked the Federal Trade Commission (FTC) to investigate Google's Buzz social networking tool for breaching privacy and trust.
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The 11 members of the US House of Representatives have called for an investigation of Buzz in an open letter to FTC chairman Jon Leibowitz.
They say the tool leaves online privacy vulnerable to unsolicited intrusion.
"Due to the high number of individuals whose online privacy is affected by tools like this - either directly or indirectly - we feel that these claims warrant the commission's review of Google's public disclosure of personal information of consumers through Google Buzz," the letter says.
The letter is the latest complaint to be sent to the FTC regarding Buzz, even though Google has made several changes in response to privacy concerns.
Despite the changes, the Electronic Privacy Information Center (Epic) said Gmail users are still automatically signed up unless they specifically opt out.
Epic, which filed a complaint with the Federal Trade Commission in February, has subsequently expanded its privacy concerns about Google Buzz.
The expanded complaint cites several examples of where there is a clear contradiction between the Gmail policy in place at the time Buzz was released and the use of Gmail account information by Google for the Buzz service.
Separately, a Gmail user is suing Google for allegedly violating data privacy laws when it launched Buzz.
Former US Navy IT manager Andranik Souvalian of Cranston, Rhode Island, claims that Google intentionally exceeded its authorisation to access and control confidential and private information.
Souvalian's complaint says that Google has unlawfully disclosed its customers' private communications and records through Buzz.