All internet and phone traffic should be recorded to help the fight against terrorism, according to one of the UK's former spy chiefs.
Civil rights campaigners have criticised ministers' plans to log details of such contact as "Orwellian".
But Sir David Pepper, who ran the GCHQ listening centre for five years, told the BBC lives would be at risk if the state could not track communication.
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Agencies faced "enormous pressure" to keep up with technology, he said.
"It's a constant arms race, if you like. As more technology, different technology becomes available, the balance will shift constantly."
The work of GCHQ, which provides intelligence on foreign and domestic threats, is so secretive that until the 1980s the government refused to discuss its existence.
