Europe’s competition regulator is preparing to move against Google Inc. in the next few weeks, a person familiar with the matter said Wednesday, setting the stage for charges against the U.S. Internet-search giant in a five-year-old investigation that has stalled three times and sparked a political firestorm.

The European Commission, the European Union’s top antitrust authority, has been asking companies that filed complaints against Google for permission to publish some information they previously submitted confidentially,...