BRUSSELS—The European Union's top advisory body on online privacy will issue an opinion this month saying that information collected by phone and Internet companies on customer locations must be treated like names, birthdays and other personal data, EU officials say.

That means smartphone giants like Apple Inc. and Google Inc. will likely have to obtain user consent before gathering the data, delete the information after a certain period of time and keep it anonymous.

The opinion, to be published by the alliance of European national regulators, called the "Article 29 Working Party," highlights the growing importance of mobile technology and the EU's position as the global leader in regulating the use of private data by tech companies. The opinion isn't binding, but it's likely to be adopted as a guiding principle by most national regulators.

The group "will say that geo-location data has to be considered as personal data," an EU official said. "The rules on personal data apply to them."