The EU's data protection authorities are concerned about the privacy effects of the policy and asked French regulator CNIL to investigate them.
CNIL said its "preliminary analysis shows that Google's new policy does not meet the requirements of the European Directive on Data Protection".
The agency said in a letter posted on its website that Google's explanation of how it will use the data was too vague and difficult to understand "even for trained privacy professionals".
The new policy makes it easier for Google to combine the data of one person using different services such as the search engine, YouTube or Gmail if they are logged into their Google account.
That allows Google to create a broader profile of that user and target advertising based on that person's interests and search history more accurately. Advertising is the main way Google makes its money.
Google argues that combining the data into one profile also makes search results more relevant and allows a user to cross-navigate between different services more easily.
"Over the past month we have asked to meet with the CNIL on several occasions to answer any questions they might have, and that offer remains open," said Peter Fleischer, Google's global privacy counsel.
"We are committed to providing our users with a seamless experience across Google's services, and to making our privacy commitments to them easy to understand."