A drive towards creating a "security state" to fight terrorism risks eroding centuries of civil liberties, the country's top prosecutor warned yesterday, in an apparent challenge to core government policies.

Sir Ken Macdonald used his final speech as director of public prosecutions to warn of the potential damage to freedoms from the government's drive to harness technology to fight terrorism. "We need to take very great care not to fall into a way of life in which freedom's back is broken by the relentless pressure of a security state," he told the inaugural Crown Prosecution Service lecture.