The policy change, implemented Thursday, means private data collected by one Google service can be shared with its other platforms including YouTube, Gmail and Blogger.
European authorities found that "transparency rules have not been applied" in changing the policies, Commissioner Viviane Reding told the BBC.
Google responded by saying it believes the new policy complies with EU law.
Google went ahead with implementing the changes despite warnings from the EU earlier this week after data regulators in France had cast doubt on the legality of the move and launched a Europe-wide investigation.
France's privacy watchdog CNIL had urged Google to take a "pause" in rolling out the revised policy.
"The CNIL and EU data authorities are deeply concerned about the combination of personal data across services," the regulator wrote.