Leading article: A dangerous erosion of individual liberty

In a democratic society, there is always a balance to be struck between citizens' safety and their right to privacy. Given the all-too-real threat of indiscriminate terrorist violence, the Government's latest plans to expand the state's powers to snoop on digital communications are understandable. But they tip the scales altogether too far.

Internet providers such as BT and Virgin Media are already required to save some information about their customers' online activities. Under new proposals expected to be included in next month's Queen's Speech, absolutely everything must be recorded: that means emails, instant messages, Skype calls, internet searches, social networking, Twitter accounts, online gaming forums, even web-browsing history. And not just for those suspected of criminal activities; for everyone.

A warrant will still be needed to access the contents of communications such as emails. But all the surrounding data – the who, what, when, where, and for how long – will be available for the police and security services not only to dredge through but also to monitor "in real time".

There are three different areas of concern here. The first is technical. Talking about gathering swathes of data from internet usage is one thing, doing it is quite another. Not only is the feasibility of collecting and storing such immense quantities of information open to question, there is also no easy way to design an interception system that will neither be easily circumvented nor need tweaking every time a third-party – Facebook, say – updates its software. Given the high failure rate of even fairly straightforward technology programmes, so ambitious a scheme, to be undertaken by any number of internet providers, begins to look unworkable.

Then there are the practicalities. How, for example, will the businesses involved pay for such far-reaching changes without adding to consumer charges? So much for the social and economic benefits of a fully networked world.

The vast data-bases produced will also present significant security risks of their own. Packed with consumer information on a wholly unprecedented scale, they will be a magnet both for hackers and for dishonest employees eager to profit from the considerable commercial potential of their contents. Indeed, even the companies themselves may be tempted to make the most of what they hold. Such concerns are as nothing, however, compared with the principle at stake.

Contrary to the Government's claims, this is no simple modernisation, no natural next step from the data collected in a telephone bill. Rather, it is a fundamental shift in the relationship between the individual and the state. Until now, that relationship has in part rested on the understanding that citizens can only be put under surveillance when a court has been convinced that there is good reason to do so. The Home Secretary's plans turn such a notion on its head. If they go ahead, surveillance will become the rule rather than the exception.

It is easy to see why the Government believes it needs new powers. With the horror of the 7/7 bombings still fresh in our minds, the consequences of terrorism are far from theoretical. Neither does the global reach of murderous terrorist ideologies show any sign of receding. In the face of such fearsome risks, Theresa May is not the first to try to increase the informational firepower available to the security services. Most likely she will not be the last. All must be resisted. So far-reaching a shift in the social contract cannot be undertaken lightly. Nor should it be rushed through in response to the fear of short-term threats, however severe. The price to be paid in the loss of individual liberty is too high. Ms May must think again.