Tony Blair today denied an accusation by a former top British diplomat that a lack of proper planning after the invasion of Iraq created a security vacuum that allowed militants to thrive.

The Prime Minister accepted that the current situation was "grim" but said that he could not take responsibility for "the people who are sending car bombs into market places".

He also denied having taken his "eye off the ball" and said that violence in the country was caused by internal and external extremists intent on destroying the wishes of most Iraqis.

In response to criticism from Sir Jeremy Greenstock, the former ambassador to the United Nations and the first British envoy to Iraq after the invasion in March 2003, Mr Blair said: The moment you remove Saddam you have a vacuum. We did indeed plan for that.

"These factions that are operating in Iraq at the moment, it's not a fault of planning. It's a deliberate attempt to thwart the will of the majority.

"We did not create al-Qaeda or the Sunni insurgency. To say that in removing Saddam we created a situation in which these groups are able to function. I don't accept that it's our responsibility. It's the responsibility of these groups themselves."

Speaking on BBC Radio 4's Today programme, a day after he announced the phased withdrawal of 1,600 British troops from Southern Iraq, Mr Blair said that the troops would return if trouble flared.

“We have the full combat capability that is there, so if we are needed to go back in in any set of circumstances, we can. The whole purpose of us being in a support role is precisely to do that,” he said.

The Prime Minister rejected claims by Sir Jeremy that following the invasion in 2003 there were no instructions to bring security back to the streets of Iraq.

Sir Jeremy, speaking in a BBC documentary, said: "No one, it seems to me, was instructed to put the security of Iraq first. To put law and order on the streets first. There was no police force. There was no constituted army except the victorious invaders."

In response, Mr Blair said: “It is true that when you removed Saddam - and his police and army, of course, were part of the establishment of oppression in Iraq - we then had to rebuild it.

"Where I don’t agree with Jeremy is that no-one was thinking about rebuilding. We actually were rebuilding.”

Mr Blair said that there was no alternative but to disband the Saddam’s security services.

He said: “There was no way that the Iraqi police force that was there under Saddam was going to be able to keep order in the country properly. They were an instrument of Saddam’s dictatorship.”

“You were always going to have to build the Iraqi police and army from scratch.”

Mr Blair said there were no plans for military action against Iran and stressed his commitment to finding a diplomatic solution to the dispute over Tehran’s nuclear programme.

He also defended his foreign policy interventions over the past 10 years, saying: “In removing the dictatorships that we have from Sierra Leone, from Kosovo, from Afghanistan and Iraq, yes, I believe the world is a better place, for the removal of those dictators.”

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