The dangers posed by terrorism should not undermine the right to a fair trial, the director of public prosecutions has said.
Sir Ken MacDonald: Urged protection of rights
Sir Ken MacDonald QC said abandoning fair trial safeguards would represent defeat and "surrender to nihilism".
His warning came in a speech to leading barristers amid expectations of a debate over counter-terrorism laws.
The UK's response to the terrorism threat should protect the institutions extremists sought to undermine.
Legislation passed by some countries in the wake of the 9/11 attacks on the United States was inconsistent and even hostile to "traditional rights", he said in a speech to the Criminal Bar Association.
"We wouldn't get far in promoting a civilising culture of respect for rights amongst and between citizens if we set about undermining fair trials in the simple pursuit of greater numbers of inevitably less safe convictions," said Sir Ken.
The DPP said political interest in crime and disorder had never been more intense.
The point where the rights of defendants and the interest of victims met was the "touchstone" for measuring if the UK was getting it right.
Sir Ken, formerly a defence barrister, said that while terrorism was not new, a distinction had to be made between previous and current threats.
"We can contrast this with the threat once posed by the IRA. I represented many of those men," he said.
"They were members of an established and highly disciplined organisation with clearly targeted enemies. They were ruthless and murderous.
"The current threat comes from unaffiliated, loose-knit networks of individuals with a much broader agenda. They think they're having a conversation with God. Killing is an end in itself.
"All the disturbing elements of a death cult psychology are present. This seems to me to be intrinsically more dangerous than what we faced previously."
But Sir Ken said the threat also carried a more subtle risk that was equally as pernicious if it encouraged a "fear-driven" response.
"By that I mean it can tempt us to abandon our values," he said. "Terrorism is designed to put pressure on some of our most cherished beliefs and institutions.
"It demands a proactive and comprehensive response. But this should be a response whose fundamental effect is to protect those beliefs and institutions, not to undermine them."
Sir Ken says the terror fight on Britain's streets is not a war
"So, although a development in the role of the security services and the police is essential and desirable in this context, I believe an abandonment of Article Six [of the European Convention on Human Rights] fair trial protections in the face of terrorism would represent an abject surrender to nihilism. It would represent defeat."
Sir Ken renewed his calls for intercept evidence such as telephone tapping to become admissible evidence in court, something the security services oppose.
But he said he was confident an agreement could be reached with the security services.
"On the streets of London, there is no such thing as a 'war on terror', just as there can be no such thing as a 'war on drugs'.
"The fight against terrorism on the streets of Britain is not a war. It is the prevention of crime, the enforcement of our laws and the winning of justice for those damaged by their infringement."