Osama Bin Laden's deputy, Ayman al-Zawahiri, has threatened to retaliate against Britain for giving a knighthood to novelist Salman Rushdie.
The 20-minute audiotape was posted on a website used by Islamic militants.
A Downing Street spokesman said: "We will not allow terrorists to undermine the British way of life."
Sir Salman's book The Satanic Verses sparked protests by Muslims around the world and led to Iran issuing a fatwa in 1989, ordering his execution.
In a 20-minute recording, the al-Qaeda second-in-command said the group was preparing a "very precise response" to the British knighthood.
Addressing Prime Minister Gordon Brown, Zawahiri said: "I say to Blair's successor that the policy of your predecessor drew catastrophes in Afghanistan and Iraq and even in the centre of London."
In the speech, entitled Malicious Britain and its Indian Slaves, Zawahiri was quoted as warning Mr Brown: "If you did not learn the lesson then we are ready to repeat it, God willing, until we are sure you have fully understood."
The UK said the knighthood was not intended as an insult to Islam
The former Egyptian surgeon, who is believed to be the architect of the al-Qaeda ideology, said Britain's award for Indian-born Sir Salman was an insult to Islam.
The UK Foreign Office said in response to the tape that the author's knighthood was a reflection of his contribution to literature.
"The government has already made clear that Rushdie's honour was not intended as an insult to Islam or the Prophet Muhammad," said a spokesman.
The Foreign Office said it would maintain efforts to thwart terrorists.
"We will continue to tackle the threat from international terrorism as a priority in order to prevent the risk of attacks on British interests at home and overseas, including from al-Qaeda," a spokesman said.