The policy is due to take effect tomorrow (1 March). Last month, Google announced plans to consolidate more than 60 different product-related privacy policies, which it said would provide users with a more intuitive experience and more relevant ads.
Yesterday, French data regulator CNIL reiterated calls for Google to pause the rollout, saying it was "deeply concerned" about the combination of data across its services, and it had "strong doubts about the lawfulness and fairness of such processing".
The UK data regulator, the Information Commissioner's Office, said its views were represented by CNIL, which was leading the response of the Article 29 Working Party group of European data regulators to Google's changes.
It said that while these authorities welcomed Google’s "large" campaign telling its users about the new policy, the search giant failed to take a "real opportunity" to consult authorities before it announced the policy in January.
It added that not all authorities were informed about the changes, while some were given a few days' notice, despite Google's claims that they had been "extensively pre-briefed."
The letter said preliminary analysis showed "the policy does not meet the requirements of the European Directive on Data Protection, especially regarding the information provided to data subjects".
It argued that because of the wide variety of Google's online services, the new policy only provided general information, making it impossible for users who were new to Google to understand how their data was being used across the services.
Google said in a statement that it had tried to meet with the CNIL on several occasions over the past month to answer any questions.
The statement said: "We believe we've found a reasonable balance between the working party's recommendations: to 'streamline and simplify' our policies while providing 'comprehensive information' to users.
"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."
The letter was sent on the same day that Eric Schmidt, Google's executive chairman, urged regulators not to restrict privacy to the point where it stifled innovation, during a keynote speech at Mobile World Congress in Barcelona.
He said: "If you have to regulate, try to regulate the outcome, not the technology. If there's an outcome that you don't like, don't specify in law a technical solution, because technology moves forward."
The latest news will come as a blow to Google, which is facing probes by regulators on both sides of the Atlantic into claims that it is anti-competitive.
Last week, Google was lambasted over privacy, after reports emerged claiming it had bypassed Apple's Safari browser privacy-protection measures, to drop cookies.
Follow Sarah Shearman on Twitter @Shearmans