The government has been accused of launching a "snooper's charter" after revealing plans to ramp up police internet-surveillance powers to snare criminals.
Under the mandate, part of the draft Communications Bill, detectives will be able to access emails, social networking profiles and web browsing history in a bid to track offenders.
But the new details will not be available to local authorities and councils will also be stripped of their current powers to access information about phone calls, the Home Secretary will announce.
Paedophiles and terrorists are the main targets of the plan, but campaigners say the rules prove a serious infringement on civil liberties.
Home Secretary Theresa May said: "Communications data is vital for the police in their fight against crime, including serious offences such as child abuse, drug dealing and terrorism.
"These measures are necessary to protect the public and investigate crime - and that is the only reason for which they should be used."
However, Rachel Robinson, policy officer for campaign group Liberty, said: "The argument for the Snooper's Charter is that we must all compromise our privacy because crime sometimes happens on the web.
"Just like the internet, any private home can be a crime scene, but should we install hidden cameras and microphones in every bedroom in the land?"