The battle against Islamist extremism must be fought on the ground, Tony Blair said as he warned that the West will not succeed without the correct strategy for tackling the growing threat.

The former prime minister, who was in power at the time of the 7/7 bombings in London a decade ago and led the country to war in Afghanistan and Iraq, stopped short of recommending that British troops should be involved in the ground battle against Islamic State (IS).

But he said that the West needed to have "the means of combating these people and combating them on the ground".

He told the BBC: "It's a global threat, it is, I'm afraid, a growing threat. But we have got ourselves to a position where it's very clear that unless we take the right policies and strategy to deal with it, we won't be able to succeed. Those require a battle of ideas and a fight against the the ideology, not just the violence but the ideology and the extremism.

"But also you have got to have the means of combating these people and combating them on the ground."

Pressed over whether the response should involve British boots on the ground, he said: "This is maybe a discussion for another day."

With the Government raising the possibility of a possible extension of the air campaign against IS to targets in Syria as well as Iraq, Mr Blair said the terror threat was not going away.

He said: "I don't criticise Western leadership today but I do say this is a long hard struggle and we've got to be prepared to engage over a long period of time because at the time of 7/7, we faced people who had been radicalised over a period of time.

"But we face a situation today where you have fighters coming back from Syria who are our own citizens. You have training camps actually in Libya not just in Syria, in Iraq and elsewhere and this threat is not going away. It will intensify in time to come."

In a separate interview, conducted by his former Cabinet colleague Dame Tessa Jowell on LBC Radio, Mr Blair denied that the UK had brought attacks such as the 7/7 atrocity on itself by joining the war in Iraq.

"One of the most important things to do here is look at this in the bigger context," he said.

"9/11 in New York was probably the first really large scale terrorist attack. Obviously, we had certain foreign policy responses to that.

"The problem is that even those countries that didn't participate in Iraq at all, like France, are now subject to these attacks.

"We have seen them most recently in Tunisia. Countries like Belgium or Norway, who are countries that have no real foreign policy presence, are also subject to this.

"This is a global problem ... and the only way of dealing with it ultimately is for people to come together whatever their faith background and say we are united against this terrorism, and to say we are not going to allow anyone to excuse themselves by saying the slaughter of totally innocent people is somehow a response to any decision by any government.

"It is the responsibility of those who carry out the attacks of terrorism and those who incite them."

Mr Blair described how he wrestled with life-or-death decisions about heeding terrorist threats in the wake of the 7/7 bombings.

The former Labour leader said one of the biggest challenges had been striking a balance between keeping the public safe and avoiding shutting down London.

Mr Blair was hosting the G8 summit in Gleneagles when news of the attacks broke in 2005.

"This was literally the day after we had won the Olympic bid for Britain. It was a moment of great euphoria for the country, for me it was a huge moment of joy and hope for the future," he said.

"I remember sitting having a bilateral discussion with the president of China when someone came in and handed me a slip of paper which said there has been an incident and you have to come out of the meeting quickly.

"I came out and then I was told about the first attacks. At the time it wasn't quite clear exactly what it was. Within 20-30 minutes it became quite clear and I spoke to Charles Clarke who was the home secretary at the time.

"As the day progressed, it became obvious that this was a severe set of terrorist attacks."

Mr Blair said his first response was to try to "bring people together" and deal with the "huge trauma" suffered by the capital.

He added: "One of the things that happens in these situations is that you get warnings and you cannot be sure if they are reliable or not. For the next few weeks we were in constant anxiety as to whether each time a warning came about whether we should shut down the Underground ...

"We thought at the time there was a distinct possibility these attacks would not be a one-off. I remember we were having meetings the whole time about whether we would be suffering another attack, whether each time we got a warning what would we do about that warnings.

"Obviously you have a duty of care to people, on the other hand if you keep shutting down the city every time there is a warning, you are going to bring it to a stop.

"It was an incredibly difficult set of decisions during that time.

"We did take one or two of the warnings very seriously and shut the Underground, or parts of it. But then we came to a point where I decided we wouldn't just keep on doing this."