Regulators in several European nations including Italy began a joint inquiry last year after Google consolidated its 60 privacy policies into one, combining data collected on individual users across its services, including YouTube, Gmail and social network Google+. It gave users no means to opt out.
In a statement on Monday, the Italian watchdog said Google's disclosure to users on how their data was being treated remained inadequate, despite the company having taken steps to abide by local law.
The watchdog gave the group 18 months to comply fully and indicated a series of measures Google must put into practice.
The Rome-based regulator said Google would not be allowed to use the data to profile users without their prior consent and would have to tell them explicitly that the profiling was being done for commercial purposes. It also demanded that requests from users with a Google account to delete their personal data be met in up to two months.
A spokesman for Google said the company had always cooperated with the regulator and would continue to do so, adding it would carefully review the regulator's decision before taking any further steps.
As part of the process, Google also agreed to present a document by the end of September that will set a roadmap of steps to comply fully with the Italian regulator's decision.
A source familiar with the regulator said should Google not comply it could risk fines of up to about 1 million euros, a tiny fraction of Google's income, as well as possible criminal proceedings. Regulators in France and Spain have already fined Google for breaking local laws on data protection, underscoring growing concerns across Europe about the volume of personal data that is held in foreign jurisdictions.
In Britain, the ICO regulator gave Google until September 20 last year to make changes to bring the policy into line with local law. On Monday a spokesman did not return a request for comment asking for an update on the case.