The Government Communication Headquarters (GCHQ) on the west of Cheltenham
David Cameron is facing a growing backbench backlash over plans for a major expansion of the Government's powers to monitor the email exchanges and website visits of every person in the UK.
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" without a warrant.
A previous attempt to introduce a similar law was abandoned by the former Labour government in 2006 in the face of fierce opposition from the Conservatives and the Liberal Democrats as well as civil liberties groups. Senior MPs from both coalition parties lined up to condemn the move by ministers to revive the plan.
The Home Office argued that the measure was "vital" to combat terrorism and organised crime and stressed a warrant would be needed in order to access the content of the communications they were monitoring.
However that did little to allay the concerns of critics who said the authorities would still be able to trace who people were in contact with and how often and for how long they were communicating.
"It is not focusing on terrorists or on criminals. It is absolutely everybody. Historically governments have been kept out of our private lives," said Conservative former shadow home secretary David Davis.
"Our freedom and privacy has been protected by using the courts by saying 'If you want to intercept, if you want to look at something, fine, if it is a terrorist or a criminal go and ask a magistrate and you'll get your approval'. You shouldn't go beyond that in a decent, civilised society but that is what is being proposed.
"They don't need this law to protect us. This is an unnecessary extension of the ability of the state to snoop on ordinary innocent people in vast numbers. Frankly, they shouldn't have that power."
Liberty director Shami Chakrabarti warned that it would undermine the coalition's commitment to human rights if it went ahead with the plan.
"There is an element of whoever you vote for the empire strikes back," she said. "This is more ambitious than anything that has been done before. The coalition bound itself together in the language of civil liberties. Do they still mean it?"