Last year, on average, people in Britain sent 35,000 e-mails a second. They also sent nearly five billion text messages a month and generated a constant, growing tide of posts, “pokes” and “twitterings” on social networking sites.

Humanity is immersed in a permanent blizzard of communication, and those fighting crime and terrorism need access to it. Since last October mobile telephony companies and internet service providers (ISPs) have been required to store data on every text, call, e-mail and web page impression and surrender it to the authorities if required. Now the Government is contemplating taking this data in-house. The next data communications Act could provide for a vast, central, state-run database recording the sender and recipient of every last digitised murmur.

The financial crisis has made this a good week for supporters of big government. Ministers may think the present mood will allow a similarly bold extension of their powers to monitor communications. If so, they are wrong.

The Home Office envisages the project becoming part of the Interception Modernisation Programme at GCHQ in Cheltenham. There are numerous practical reasons why it should not. The first is cost: £1 billion has reportedly been earmarked for the database, but the long-term cost of running it is likely to be far higher. As the global financial crisis lays waste to public finances, it is hard to see where the money will be found.

Secondly, the temptations for government agencies to misuse such a database - and for terrorist and criminal organisations to gain access to it - would be immense. Thirdly, the Government's record on data security is appalling. Large government IT projects involve multiple layers of contractors and civil servants, and their inability to keep track of sensitive laptops and CDs would be comical if it were not so serious.

The authorities cite at least as many practical arguments in favour of the database. Ninety-five per cent of serious crime investigations involve communications data, which has also proved critical in terrorism prosecutions. But the overall volume of digital communications is rising exponentially, and police and the security forces fear they cannot keep track of all of it under existing legislation. They worry in particular about little-known ISPs providing cover for clandestine communication networks by failing to store data as required; and about individuals vanishing behind assumed online identities.

Jacqui Smith, as Home Secretary, is personally responsible for the struggle against terrorism. She could, therefore, be forgiven for losing sight of what she calls “the right balance” between security and civil liberty - if that balance were not so central to the British way of life.

The security forces already have ample monitoring powers. As in the debate on 42-day detention without trial, the Government has been unable to point to a single case in which the greater powers it seeks would unquestionably have made the public safer. This proposal has the arguable merit of being debated at leisure, not in haste. But it amounts to a leisurely stroll from a nanny state to a headmaster state, in which citizens give up essential elements of their independence for protection against a pervasive but ill-defined threat - and in which clichés about Big Brother become all too valid.