The Liberal Democrat leader, Charles Kennedy, tonight sparked anger in the wake of the London bombings by blaming the Iraq war for increasing terrorism.

He said there was no "causal link" between British involvement in the invasion and last week's attacks on the capital.

But he was branded "deeply irresponsible" after saying the prime minister, Tony Blair, and the US president, George Bush, should not be surprised if people drew a link between the war and terror attacks on the UK.

He claimed the war had "fuelled the conditions in which terrorism flourishes", and warned terrorists would use the war as "fodder" for recruitment.

The Tories likened Mr Kennedy to those who tried to appease Hitler.

Politicians from all main parties have gone to great lengths to avoid linking the London attacks with the war. Anti-war Respect MP George Galloway sparked outrage last week when he said Londoners had "paid the price" for invading Iraq.

Defence minister Adam Ingram accused him of "dipping his poisonous tongue in a pool of blood".

The prime minister rejected the claim by pointing out that the 9/11 atrocities in the US happened before the Iraq war.

Speaking at the weekend Mr Kennedy, who opposed the war from the outset, said there was no connection between it and the London attacks.

But in a keynote speech at London's Institute of Contemporary Arts Mr Kennedy said: "Those, like President Bush and Tony Blair, who have sought to link Iraq with the so-called 'war on terror' can hardly be surprised when members of the public draw the same link when acts of terrorism occur here in the United Kingdom.

"And the terrorist certainly will not shrink from using Iraq to increase resentment and as fodder for recruitment."

Mr Kennedy added: "The way we went to war in the first place, as well as the mismanagement of the aftermath, have fuelled the conditions in which terrorism flourishes."

He said the war had created an unstable Iraq, which was a "training ground" for terrorists.

The Lib Dem leader pointed to intelligence chiefs' warnings that the war risked increasing the threat of terrorism.

He added: "I am not here implying some causal link between Britain's involvement in Iraq and the terrible terrorist attacks in London last week. Not at all.

"The mass murderers who attacked London last week did not need Iraq as an excuse. The blame for the deaths in London falls firmly on their shoulders and on their shoulders alone."

The shadow defence minister, Julian Lewis, condemned Mr Kennedy. "This is a deeply irresponsible statement," he said.

"It was not the Iraq war which started acts of terrorism by al Qaida. You cannot say we were wrong to take on the terrorists or that we would be immune from terrorist attack if we did not.

"What he seems to be saying is keep your head down and hope you will not be attacked as long as you do nothing to offend the terrorists.

"That is exactly the policy of appeasement people used to use in the face of threats from other totalitarian movements in the 1930s.

"Churchill said appeasement was a policy of throwing others to the alligator in the hope that it will eat you last. That appears to be Mr Kennedy's policy."

Labour backbencher David Winnick also turned on Mr Kennedy. "It is very important that politicians - and even more - those who lead political parties - are careful," he said.

"Otherwise the impression may be given, however much they would wish otherwise, that terrorists have a justified cause. The fact of the matter is even without Iraq there would be other reasons why terrorists would strike at this country."

Downing Street also criticised Mr Kennedy's comments. The prime minister's official spokesman pointed to terror attacks before the Iraq war.

"I think it is naive frankly to believe that you can say that that kind of terrorism is due to the Iraq war," he said.

"It existed before Iraq, the organisation, the mindset that supported that kind of terrorism existed before the Iraq war, and therefore to put it down to the Iraq war, I think, is misplaced."

He added: "Nobody should do anything that suggests that there is any responsibility for the London atrocities other than by those who carried them out."

Later, Mr Kennedy told BBC Radio 4's PM programme that Britain's intelligence services had been worried for a considerable period about UK citizens "who may have been flitting in and out of Iraq, learning terrorist techniques".

But he went on to say: "That is not in any way, as I made very plain in the speech, in any way to say that there is some kind of direct causal link between what happened in London and the situation in Iraq.

"I think there is no doubt that London, and the UK generally, is an international target for terrorism, as we know. And that situation is not about to change, sadly.

"Therefore what the responsible attitude, in terms of British politics, must be, is to separate quite clearly in people's minds the awfulness of what took place in London, the fact that Iraq provides no blanket cover for any apologists in terms of what their views may have been about the Iraq war, but nonetheless to bear in mind that it is the unsettled position within Iraq and the Middle East generally that is proving such a hard nut to crack and is giving greater succour and encouragement to would-be terrorists."