Ministers are preparing a major expansion of the Government's powers to monitor the email exchanges and website visits of every person in the UK, it has been reported.
Under legislation expected in next month's Queen's Speech, internet companies will be instructed to install hardware enabling GCHQ - the Government's electronic "listening" agency - to examine "on demand" any phone call made, text message and email sent, and website accessed in "real time", The Sunday Times reported.
A previous attempt to introduce a similar law was abandoned by the former Labour government in 2006 in the face of fierce opposition.
However ministers believe it is essential that the police and security services have access to such communications data in order to tackle terrorism and protect the public.
Although GCHQ would not be able to access the content of such communications without a warrant, the legislation would enable it to trace people individuals or groups are in contact with, and how often and for how long they are in communication.
The Home Office confirmed that ministers were intending to legislate "as soon as parliamentary time allows".
"Communications data includes time, duration and dialling numbers of a phone call, or an email address. It does not include the content of any phone call or email and it is not the intention of Government to make changes to the existing legal basis for the interception of communications," s spokesman said.
Nick Pickles, director of the Big Brother Watch campaign group, said: "This is an unprecedented step that will see Britain adopt the same kind of surveillance seen in China and Iran. This is an absolute attack on privacy online and it is far from clear this will actually improve public safety, while adding significant costs to internet businesses."
Shami Chakrabarti, director of the civil rights group Liberty, said Conservatives and Liberal Democrats had resisted the plan in opposition. "It is a pretty drastic step in a democracy. It was resisted under the last government. The coalition bound itself together in the language of civil liberties. Do they still mean it?" she said.
Conservative backbencher Margot James said ministers would come under pressure to water down the proposals as the legislation passed through Parliament.