Foreign Secretary Jack Straw has described terrorism as the "new totalitarianism" which is the world's greatest threat to democracy.
Jack Straw compared terrorism to totalitarian regimes
Speaking at Labour's spring conference, he warned delegates not to be slow to recognise the danger, as some had been to totalitarian regimes of the past.
"In both its tactics and its intent, it seeks... to destroy the principles and values we all hold dear," he said.
He spoke as the death toll from this week's bombings in Madrid rose to 200.
Mr Straw told the Manchester conference: "We still do not know precisely who or what was responsible for such evil in Madrid.
"But I do know that the target was a wider one than the poor poeple whose lives have been so cruelly cut short this week.
"For let us be in no doubt, this was an attack on the very foundations of our democratic way of life."
He compared terrorism to the regimes which led to dictatorships in many parts of Europe earlier this century.
"Today, the greatest threat to human freedoms and human rights is terrorism," he said.
"Terrorism is the new totalitarianism...
"We cannot and must not be slow to recognise the dangers of the new totalitarianism today," he said.
He added that it was only by co-operation across Europe "that we can defeat
the new forces of evil that threaten us today - we can, and we will".
The prime minister also opened his speech to the conference by describing terrorism as the "new menace of our time", and comparing it to totalitarian communism.
Earlier on Saturday Europe minister Denis MacShane urged the UK to stop discussing the reasons for going to war in Iraq and join the rest of the continent in "unity" against terrorism.
The presence of so many EU leaders - including British deputy prime minister John Prescott - on Madrid's anti-terror march on Friday
made it an unprecedented display of European fellow-feeling, he said.
"It was a very powerful political message that terrorism is not going to