In a letter addressed to Google CEO Larry Page, data regulators from 27 EU countries call on Google to provide users with more information on what data it collects and for what purpose.
* It's not clear enough in explaining to users what data is collected and how it will be used
* It's too difficult for users to opt out of data collection
* It doesn't day how long Google will hold on to the collected user data
"As data protection regulators, we expect that Google takes the necessary steps to improve information and clarify the combination of data, and more generally ensure compliance with data protection laws and principles," the letter said.
CNIL warned Google that in case no action was taken to alley its concerns, it would "enter a phase of litigation" against the internet giant.
Google's global privacy counsel, Peter Fleischer, reacted to the letter in a statement on Tuesday.
"We are confident that our privacy notices respect European law," he added.
Pro-privacy campaigners welcomed the letter from EU regulators.
Nick Pickles, director of privacy campaign group Big Brother Watch, said: "Unless people are aware just how much of their behavior is being monitored and recorded, it is impossible to make an informed choice about using services."
The news comes as regulators on both sides of the Atlantic are preparing for possible major antitrust cases against Google. These are centred on allegations that Google may have abused its dominant position in search to promote its own services over and above those of competitors to gain an unfair competitive advantage.