Western democracies have been "outspent, outmanoeuvred and out-strategised" by violent Islamist extremists, Tony Blair has claimed.
In a speech in New York, the former British prime minister said that warnings over the past week of terrorist plots against Europe should remind people that they remained under threat.
Mr Blair said a "narrative" that Muslims were under attack from the US and its allies, who acted out of support for Israel, had been allowed to take hold, aided by "websites and blogs".
A fresh confrontation was needed because it would be impossible to defeat extremism "without defeating the narrative that nurtures it", he said.
"The practitioners of extremism are small in number. The adherents of the narrative stretch far broader into parts of mainstream thinking," Mr Blair told the Washington Institute for Near East Policy.
"It is a narrative that now has vast numbers of assembled websites, blogs and organisations."
Mr Blair said it was "absurd" that some people were surprised at how powerful Islamist extremist groups were, given the amount of funding they received.
"Measure, over the years, the paucity of our counter-attack in the name of peaceful co-existence," he said. "We have been outspent, outmanoeuvred and out-strategised."
Mr Blair said a tendency to "sympathise" with extremism was disempowering for moderate Muslims, because it made people resent them.
Mr Blair also defended the invasion of Iraq and Afghanistan, saying: "Whatever you think of the original action, we enabled the people to choose their government." (© Daily Telegraph, London)