Tony Blair was yesterday blamed for the London suicide bombings by al Qaida as the terror network vowed there would be more horror and carnage in Britain.

In a video message, Osama bin Laden's deputy, Ayman al-Zawahiri, said the Prime Minister's policies in Iraq and Afghanistan were the reason for the attacks.

He said: "Blair has brought to you destruction in central London and he will bring more of that, God willing."

In the first message from the al Qaida leadership since the bombings, al-Zawahiri was shown seated with a rifle resting on a wall behind him.

The tape was broadcast by Arab television network al-Jazeera on the four-week anniversary of the July 7 suicide attacks, in which 52 commuters died. It is being examined for clues by the intelligence services but appeared to offer no hint about the location of al-Zawahiri's hideout.

The 54-year-old Egyptian physician, who founded the Egyptian Islamic Jihad movement before allying with bin Laden in the late 1990s, has had a $25m bounty (£14.2m) put on his head by the US government.

He was shown repeatedly jabbing his finger as he also promised that the US would suffer even worse casualties in Iraq in the future.

"There is no way out of Iraq without immediate withdrawal, and any delay on this means only more dead, more losses," he said.

He threatened further attacks on any Western nation, including Britain, which has contributed troops to the US-led force in Iraq.

Those nations had ignored a three-month "truce" offered by bin Laden to European nations in April last year to give them time to withdraw their troops from Iraq, he said.

"Instead, you spilled blood like rivers in our countries and we exploded the volcanoes of wrath in your countries," al-Zawahiri said.

"Our message is clear - you will not be safe until you withdraw from our land, stop stealing our oil and wealth and stop supporting the corrupt rulers."

Downing Street and Scotland Yard made no comment on the video and al-Jazeera did not say how it was received.