Britain said on Thursday it would rush through emergency legislation to force telecoms companies to retain customers' data for a year, saying the move was vital to protect national security following a decision by Europe's top court.
Communication companies had been required to retain data for 12 months under a 2006 European Union directive which was thrown out in April by the European Court of Justice which said it infringed human rights.
The scrapping of the directive could deprive police and intelligence agencies of access to information about who customers contacted by phone, text or email, and where and when, the British coalition government said.
Such information had been used by the security services in every counter-terrorism investigation in the last decade, and it was vital these powers were not compromised when there was growing concern over Britons travelling to Iraq and Syria to join militant Islamist groups, the government added.
Prime Minister David Cameron stressed the emergency law would only restore existing powers and enshrine them in law, ensuring investigations would not be hampered and giving protection to the telecom firms from possible legal challenges.
The measures would not give the authorities any new powers to access Britons' personal data or the content of their calls or emails, he added.
"No government introduces fast track legislation lightly. But the consequences of not acting are grave," Cameron said in a
"I want to be very clear that we are not introducing new powers or capabilities - that is not for this Parliament. This is about restoring two vital measures ensuring that our law enforcement and intelligence agencies maintain the right tools
to keep us all safe."
The emergency security legislation, which has the support of all three major parties, will include a termination clause meaning it will expire in 2016, forcing lawmakers to look at the measures in detail again before then.
The measures come in the wake of revelations by former US intelligence contractor Edward Snowden about the British authorities' snooping activities, and privacy campaigners said they were worried about the implications of the new law.
"It is a basic principle of a free society that you don't monitor people who are not under suspicion," Emma Carr, acting director of Big Brother Watch said in a statement.
"We need to get back to a point where the police monitor people who are actually suspected of wrongdoing and rather than wasting millions every year requiring data to be stored on an indiscriminate basis."
The government said the proposed legislation would establish a Privacy and Civil Liberties Oversight Board, based on a US model, to ensure civil liberties were properly taken into account in counter-terrorism policies.
It also said the number of bodies that could approach telecoms and internet firms for data would be restricted, and there would be an annual transparency report to make information more widely available on surveillance powers used by the state.
The government failed last year to bring in a Communications Data bill, dubbed a "snoopers charter", which would have secured the West's most far-reaching surveillance powers in the face of widespread opposition.
Senior police and security chiefs had argued that unless they were given new powers to monitor online activities, militants and crooks would exploit new forms of communication technology such as Facebook and Skype.
Deputy Prime Minister Nick Clegg, leader of the centre-left Liberal Democrats, the junior partner in the coalition government, blocked those plans saying they were not proportionate or workable.
But he backed the new emergency legislation. "We know the consequences of not acting are serious, but this urgency will not be used as an excuse for more powers, or for a 'snooper's charter'," he said.