Tony Blair has denied that military intervention in the Middle East has radicalised Muslims and encouraged them to engage in acts of terrorism.
The former prime minister said the fight against Islamic terrorism would only end "when we defeat the ideology".
And Mr Blair said the death of Osama bin Laden was "immensely important".
Speaking to the BBC, Mr Blair also revealed he once almost had to order a passenger jet to be shot down over UK airspace in the wake of 9/11.
In an interview with Radio 4's Today programme, marking 10 years since the 9/11 attacks, the former prime minister said: "The reason why these people are radicalised is not because of something we're doing to them. They believe in their philosophy.
"I see this out in the Middle East all the time. There is this view, which I'm afraid I believe is deeply naive in the West, that somehow these people, you know, misunderstand our motives, that we've confused them, that that's why they've become radicalised.
"Understand one thing - they believe in what they believe in because they believe their religion compels them to believe in it."
Mr Blair added that he did not believe the provision of democracy in Middle Eastern countries "by the way a process, as I say, not imposed as an act of imperialism should radicalise anybody.
"And until we stop accepting that somehow we, by our actions, are provoking these people to be as they are, we will carry on with this problem."
He went on to say that people in Iraq and Afghanistan wanted democracy and that this ideology was not being imposed on them.
"The Taliban party or the Saddam party could have come and won the elections. The fact is the people in those countries were glad to see the back of them. Now what they want is to see the back of the terrorism."
Mr Blair also said that while Bin Laden's death had dealt a blow to al-Qaeda, the fight against terrorism was not "just about one man".
Continue reading the main story “Start QuoteThere was a moment later in my premiership where we were really not very far away from having to take a final decision as to whether to bring the plane down”
End Quote Tony Blair
Bin Laden, widely thought to have been the 9/11 mastermind, was shot dead in Pakistan by US forces in May. He had been on the run since 2001.
In an interview with the Reuters news service, Mr Blair said: "The risk is still there, but we have gone after them [al-Qaeda]. We have degraded a lot of their capacity and capability. We have either captured or killed many of their leading people."
He added that, although there had been "significant advances, the struggle still goes on".
Mr Blair said: "I think the narrative and the ideology of the movement is still there. So killing him [Bin Laden] was actually immensely important.
"It dealt a huge psychological blow to their movement but it doesn't alter the fact there are still large numbers of people out there who buy the narrative of this terrorist movement, even if they do not share or even agree with the methods."
He also said the war against terrorism would only end when the ideology was defeated, and that this battle would continue for a generation.
"The way to defeat this ideology ultimately is by a better idea, and we have it, which is a way of life based on openess, democracy, freedom and the rule of law."
But Lord West, who was a security minister in Gordon Brown's government, said Mr Blair "was wrong" about his views on radicalisation.
He told Sky News: "There's no doubt that the invasion of Iraq had nothing to do with a terrorist threat to this country.
"There's no doubt that foreign policy does impact on radicalisation. It is not the sole cause. I'm afraid prime minister Blair was wrong in thinking it didn't impact, because it does."
Mr Blair, who is now a Middle East peace envoy, recalled when he first found out that the World Trade Center in New York had been attacked.
He said: "I was preparing to give a speech to the Trades Union Congress in Brighton. I was in my hotel room. I was then interrupted by one of my aides who said 'Come and see what's happening on the television'. The first plane had already flown in and hit the tower.
"I was actually very, very clear right from the very outset that this was not just a terrorist attack of an extraordinary magnitude but one that had to change global policy. So really everything that followed from that, in a sense, followed from that event."
Mr Blair remained a close ally of then US President George W Bush as he launched a "war on terror", sending UK troops on US-led invasions of Afghanistan in 2001 and Iraq in 2003.
Mr Blair has been criticised in recent weeks for his links to Colonel Muammar Gaddafi, the Libyan leader who was ousted last month amid allegations of widespread human rights abuses.
But the former prime minister defended his government's decision to restore normal relations with the regime in 2004.
He said: "The external policy of Libya changed. They gave up their chemical, nuclear weapons programmes.
"It was a great thing for the world, really important. They gave up sponsoring terrorism, co-operated in the fight against it.
"The trouble is, in the end they were not prepared to reform internally, to their people. So they were less of a threat to the outside world, but inside, they were a threat to their people."
Mr Blair said that military force should be considered to stop Iran developing a military nuclear programme.
"I don't think it would include invasion but I think you cannot rule out the use of military force against Iran if they continue to develop nuclear weapons in breach of the international community's obligations on them."
And he revealed how there was an incident some time after 9/11 when a passenger jet in UK airspace was deemed a potential threat, because it was not responding to air traffic control.
"There was a moment later in my premiership where we were really not very far away from having to take a final decision as to whether to bring the plane down," he said
"I ended up talking directly to the officer who was in charge of the operation and trying to work out whether the plane in question had [encountered] a mishap, which obviously was the overwhelming likelihood, but what if it wasn't?
"It was an extremely frightening moment."
He also said that fighter jets had been "prepared" in readiness to intercept the jet, which was later found not to be a threat.