UK information commissioner Christopher Graham has joined Canada, France, Germany, Spain and five other national privacy regulators in calling on Google to adopt stricter controls for Buzz.
The regulators said Buzz showed a "disappointing disregard for fundamental privacy norms and laws", in a letter to Google chief executive Eric Schmidt.
They also charged that privacy concerns were being forgotten as Google introduces an increasing number of inter-connected web services.
The privacy regulators called on Google to incorporate fundamental privacy principles into the design of all new services.
Although the letter does not threaten any action, it represents a shot across the bow for Google, according to the Financial Times.
The letter also reflects growing concerns about the power of Google and its mission to make all information searchable, according to The Guardian.
Google has responded to the letter by saying the company tries to be transparent about what data it collects and build meaningful controls into its products.
But the firm conceded that it did not always get everything 100% right.
In March, a group of US congressmen asked the Federal Trade Commission (FTC) to investigate Google's Buzz for breaching privacy and trust.
The congressmen called for an investigation of Buzz, saying the tool leaves online privacy vulnerable to unsolicited intrusion.
Google has subsequently told the FTC that it will support self-regulatory standards and a federal privacy law that will establish baseline privacy protections.
Despite several changes by Google in response to privacy concerns, 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 FTC in February, expanded its privacy concerns about Google Buzz in March.
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.
This article was first published by Computer Weekly