The National Association of Attorneys General sent a letter to Google chief executive Larry Page arguing that the new policy "appears to invade consumer privacy" by sharing personal information between services that people rely on.
Google announced the change to its terms of service in January, explaining that it will essentially "treat you as a single user across all our products" when it comes to use patterns tracked for targeting services, content or ads.
"On a fundamental level, the policy appears to invade consumer privacy by automatically sharing personal information consumers input into one Google product with all Google products."
The Electronic Privacy Information Centre two weeks ago asked a federal court to block Google from implementing the change on March 1 as planned and to direct the Federal Trade Commission to intervene.
The updated policy will make Google privacy practices easier to understand, and it reflects a desire to create a "seamless experience for our signed-in users", Google said in response to an inquiry.
"We've undertaken the most extensive notification effort in Google's history, and we're continuing to offer choice and control over how people use our services," said a spokesperson for the California-based company.
"Of course we are happy to discuss this approach with regulators globally."
People may have reasons to keep information such as Gmail use separate from web surfing habits noticed by Google's search engine or Chrome browser software, the attorneys general maintained.
The letter was sent on the same day that California attorney general Kamala Harris announced an agreement with Google, Apple, Microsoft, Amazon, Hewlett-Packard and BlackBerry-maker Research In Motion to strengthen the privacy of people who use "apps" on smartphones or tablet computers.
The companies agreed to require applications made for mobile devices on their competing technology platforms to provide privacy policies if mini-programs collect personal information, according to Harris.
""This agreement strengthens the privacy protections of... millions of people around the globe who use mobile apps," Harris said.
"By ensuring that mobile apps have privacy policies, we create more transparency and give mobile users more informed control over who accesses their personal information and how it is used."