Coalition plans to expand the powers of the security services to monitor emails and phone calls will give them "unfettered access to every single communication" people send, a senior Tory MP has warned.
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.
Under the new plans the security services would still require a warrant to read the contents of any intercepted emails of phone calls, but they would be able to examine who sent what to whom, when it was sent, and how long the communication lasted.
Speaking on BBC Radio 4's Today programme on Monday morning, former Tory leadership candidate and shadow home secretary David Davis dismissed the idea that the proposed law would not enable GCHQ to snoop on the content of emails and phone calls.
"Your web address is content, if you access a web[site] it's content," he said. "It's a very very big widening of powers that will be very much resented by very many citizens".
The plan has also been criticised for being at odds with the promise in the coalition agreement that the Conservatives and Liberal Democrats would "reverse the substantial erosion of civil liberties under the Labour Government and roll back state intrusion".
The document that forms the basis of the governing agreement between the two parties also pledges to end the "storage of internet and email records without good reason".
Senior MPs from both coalition parties have lined up to condemn the move by ministers to revive the plan, denouncing it as an unnecessary extension of the state's powers to "snoop" on its citizens.
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 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."
Mark Field, a Conservative member of the the parliamentary Intelligence and Security Committee, which oversees the work of the intelligence agencies, said he believed that opposition had grown since the last attempt to legislate.
"I would imagine that if anything the sentiment has become even stronger among MPs across the House that they would be extremely concerned if this were to see the light of day in legislation in this entirely unvarnished way," he told BBC Radio 5 Live's Pienaar's Politics.
"I think the notion of having a warrant and having this done through an open and transparent legal process is one that has worked well and I hope that it will work well in the future."
The senior Lib Dem MP Malcolm Bruce, also speaking on Pienaar's Politics, warned that the system could be wide open to abuse.
"The problem we have had in the past is this information has been leaked, lost, stolen. I think there would be very, very real concerns that it could be open to all kinds of abuse.
"We have had a situation where police have been selling information to the media. I think we are in a very, very dangerous situation if too much information is being passed around unnecessarily."
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 told Sky News's Murnaghan programme.
"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?"
A history of the rise of the surveillance state over the past decade:
The Home Office, however, said it was essential that the police and security services were able to access communications data and that ministers would be bringing forward legislation "as soon as parliamentary time allows".
"It is vital that police and security services are able to obtain communications data in certain circumstances to investigate serious crime and terrorism and to protect the public. We need to take action to maintain the continued availability of communications data as technology changes," a spokesman said.
"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."
Liberal Democrat leader and deputy prime minister Nick Clegg sought to calm fears that the plan went against the core beliefs of his party.
"I am totally opposed to the idea of governments reading people's emails at will or creating a new central government database," he said.
"The point is we are not doing any of that and I wouldn't allow us to do any of that.
"I am totally opposed to it as a Liberal Democrat and someone who believes in people's privacy and civil liberties.
"All we are doing is updating the rules which currently apply to mobile telephone calls to allow the police and security services to go after terrorists and serious criminals and updating that to apply to technology like Skype which is increasingly being used by people who want to make those calls and send those emails."
Nick Pickles, director of the Big Brother Watch campaign group, said: "No amount of scare-mongering can hide the fact that this policy is being condemned by MPs in all political parties.
"The government has offered no justification for what is unprecedented intrusion into our lives, nor explained why promises made about civil liberties are being casually junked.
"The silence from Home Office ministers has been deafening. It is remarkable that they wish to pry into everything we do online but seem intent on avoiding any public discussion."
The government's former independent reviewer of terrorism legislation, Lord Carlile, said he expected parliament to demand strict safeguards on any new powers but he told the BBC Radio 4 Today programme the proposals were about updating existing regulations.
He said: "There is nothing new about this. The previous government intended to take similar steps and they were heavily criticised by the coalition parties.
"But having come into government, the coalition parties have realised this kind of material has potential for saving lives, preventing serious crime and helping people to avoid becoming victims of serious crime.
"Parliament will apply the most anxious scrutiny to any proposed legislation of this kind.
"We are talking about the updating of existing practices.
"When I was independent reviewer of terrorism legislation, I looked at this issue for the last government and I suggested there should be an independent board which scrutinised all this activity and ensured it was not simply the police or the security services that makes these decisions but they were properly, independently monitored - and that is what I expect parliament to demand.
"There is actually very little, if any, evidence known to me to show current powers have been used improperly.
"I agree we do need to ensure there is proper independent scrutiny, maybe of a much more substantial kind than exists at the moment to ensure these powers, when they are used, they are used proportionately. What we have to protect the public from is arbitrary action by the government or any government authority."