Peter Fleischer, Google's privacy lawyer, has told BBC News the global search engine "could do better" with policy statements that explained why user data was sometimes shared with third parties. However, Fleischer said Google never gives "identifiable personal data" to third parties or advertisers.
Interest in Google's privacy policy has heightened because of a working party of European Information Commissioners asking Google to explain why it keeps web user history for up to two years.
Fleischer said: "We will never transfer to third parties, including advertisers, any personally identifiable information about our users. Our goal is to be as transparent as possible with our users when it comes to privacy. That transparency builds trust and we will succeed or fail on whether our users trust us."
Concern has been raised about the implications of Google's acquisition of online advertising firm DoubleClick, which helps link ad agencies and web publishers. Some in the industry and campaigners have argued that between the two companies, they have unprecedented information on consumer's web habits.