External estimates of the cost of the superdatabase have been put as high as ?12bn, twice the cost of the ID cards scheme, and the consultation paper, to be published towards the end of next month, will include an option of putting it into the hands of the private sector in an effort to cut costs. But such a decision is likely to fuel civil liberties concerns over data losses and leaks. Macdonald, who left his post as DPP in October, told the Guardian: “The tendency of the state to seek ever more powers of surveillance over its citizens may be driven by protective zeal. But the notion of total security is a paranoid fantasy which would destroy everything that makes living worthwhile. We must avoid surrendering our freedom as autonomous human beings to such an ugly future. We should make judgments that are compatible with our status as free people.”

Maintaining the capacity to intercept suspicious communications was critical in an increasingly complex world, he said. “It is a process which can save lives and bring criminals to justice. But no other country is considering such a drastic step. This database would be an unimaginable hell-house of personal private information,” he said. “It would be a complete readout of every citizen’s life in the most intimate and demeaning detail. No government of any colour is to be trusted with such a roadmap to our souls.”

The moment there was a security crisis the temptation for more commonplace access would be irresistible, he said.

Other critics of the plan point to the problems of keeping the database secure, both from the point of view of the technology and of deliberate leaks. The problem would be compounded if private companies manage the system. “If there is a breach of security in that database it would be utterly devastating,” one said.