More than 300 European MEPs are backing a plan that would force search engines such as Google to store details of web searches for up to two years.
Two MEPs drew up the plan to help authorities develop an "early warning system" against paedophiles and sex offenders who were using the internet. However, civil liberties groups immediately criticised the proposals, which would represent a major increase in the monitoring of online activity.
Written Declaration 29, which has won the backing of 324 MEPs, would extend existing legislation which obliges internet service providers to retain basic session data for up to two years. The European Commission will have to examine the proposal should it win the backing of 369 MEPs, but it will be under no obligation to make it law.
Privacy International, the civil liberties group, said it was "deeply concerned" about the declaration: "While we support initiatives that are carefully and sensitively designed on the basis of a lawful and rational foundation, this proposal appears to us to be both illegal and counter-productive.
"It is not acceptable or appropriate to dissolve the fundamental right to privacy on the basis of an utterly incoherent argument that it will protect our children – when clearly it will ultimately fail to meet such a mandate."