Google is currently being investigated by the US Federal Trade Commission, and could also face a European Union investigation, over its $3.1bn acquisition of banner advertising serving company DoubleClick. The company's rivals, including Microsoft, complained the acquisition was anti-competitive and would give it excessive access to consumer and marketing data.
Its policy change - announced this week and set to be enacted over the next few weeks - means that cookies from its sites will be deleted from a person's computer after two years. However, when a user returns to the site the cookies will be updated.
Peter Fleischer, Google's global privacy counsel, said: "After listening to feedback from our users and from privacy advocates, we've concluded that it would be a good thing for privacy to significantly shorten the lifetime of our cookies."