Members of the European Parliament have been pressing for a declaration that could force search engines to keep track of users' web requests - and, if necessary, hand the data over to police.
The aim of the Data Retention Directive is to help tackle online child abuse.
However, many campaigners have expressed concern about its privacy implications.
Over 324 MEPs have already signed the declaration, which would be adopted by the European Parliament, should it receive 369 signatures.
The move comes at the same time as the EU has been putting pressure on companies such as Google to cut the amount data they hold on website users, and anonymise it for privacy reasons.
