Search engines should delete personal data held about their users within six months, a European Commission advisory body on data protection has said.
The recommendation is likely to be accepted by the European Commission and could lead to a clash with search giants like Google, Yahoo and MSN.
Google and Yahoo anonymise user data after 18 months, while MSN does the same after 13 months.
The body said search companies were not clear enough on data protection.
Google said its privacy policy "strikes the right balance" between privacy, security and innovation.
No-one from Yahoo or MSN was immediately available for comment.
Peter Fleischer, Google's global privacy counsel, said in a statement: "Google takes privacy incredibly seriously; protecting our users' privacy is at the heart of all our products.
