Ayman al-Zawahri's 20 minute speech was entitled Malicious Britain And Its Indian Slaves.

It was produced by as-Sahab, the multimedia wing of al Qaida, to be distributed to extremist websites, said the US-based SITE intelligence group, which monitors al Qaida messages.

The authenticity of the tape could not be independently confirmed.

Osama bin Laden's deputy lashed out at Britain for having awarded a knighthood to Rushdie last month, saying it was defying the Islamic world by granting the honour to the author of The Satanic Verses, deemed to insult Islam.

A "very precise response" is in preparation to retaliate against this offence, al-Zawahri was quoted as saying by SITE.

Addressing Prime Minister Gordon Brown, the al Qaida deputy chief said Britain's strategy in the Middle East "has brought tragedy and defeat upon you, not only in Afghanistan and Iraq but also in the centre of London."

"And if you did not understand, listen, we are ready to repeat it for you," al-Zawahri was quoted as warning Mr Brown.

Rushdie was awarded a knighthood by the Queen last month to honour his career as a writer. The decision stirred anger among Muslim radicals, some groups renewing calls for the novelist to be sentenced to death.

Downing Street later said the British way of life would not be undermined by terrorists. A spokesman said: "We do not intend to dignify this with a response. As the Prime Minister has said we will not allow terrorists to undermine the British way of life. The British people will remain united, resolute and strong."