Tony Blair is expected to give details this morning of proposals to widen the British Government's powers to deport and the block the entry of preachers and extremists who encourage terrorism in the UK.

The Prime Minister will not announce any new powers, rather a clarification and extension of rules that already allow Charles Clarke, the Home Secretary, to remove individuals from Britain if they are deemed a security threat.

In the days after the London bombings, the Commissioner of the Metropolitan Police, Sir Ian Blair, asked for new rules to proscribe "glorifying terrorism" and to make it easier to prosecute what he called "preachers of hate".

This morning, Sir Ian welcomed the proposed expansion of powers: "It may have been better if it was done before, but let’s do it now," he told GMTV.

Sir Ian also said that he believed that there was now more public support for rules to govern the behaviour of provocative preachers and extremists. In the past, critics have warned that preachers will be imprisoned and persecuted in their home countries if they are removed from Britain.

"One of the difficulties has been this idea about how can we deport people to places where they may suffer oppression," he said. "Well, I think the public mood is shifting. I’m sorry, but this is England, Britain, and we don’t want this fomenting of terrorism to go on."

In recent weeks, the Home Secretary has spoken of his intention to find new ways to "deal with those who foment terrorism or seek to provoke others to terrorist acts".

Last month, Mr Clarke told MPs that he was planning to use his existing powers "more widely and systematically" to stop dangerous preachers from entering Britain and to deport those already here.

The Home Secretary said he hoped to have the ability to remove individuals who come to Britain as visitors, students, workers and asylum applicants. Those who have already won asylum could have their right to remain in the UK overturned if they incited terrorism, he warned.

To enforce the increased powers, the Home Office will use a database of of individuals who have demonstrated "unacceptable behaviour" that encouraged terrorism. The database will be built from information from the police, Foreign Office and intelligence agencies .

The proposals are separate from the Government's new Counter Terrorism Bill, which will be put before Parliament in October, and will not require new legislation.

At today’s press conference in Downing Street, the Prime Minister is also expected to respond to the videotaped message of Ayman al-Zawahiri, the second-in-command to Osama bin Laden, that was broadcast on al-Jazeera yesterday afternoon.

In the video, al-Zawahiri said that Britain was paying the price for supporting the United States in the war in Iraq and that the London bombings were a direct consequence to policies enacted by Mr Blair.

"Blair has brought you destruction to the heart of London, and he will bring more destruction, God willing," said the video.

Jabbing his finger at the camera and sitting next to a large gun, Zawahiri chided the British for rejecting the "truce" offered by bin Laden in 2004 and broadened al-Qaeda’s agenda to demand that the West give up all political and economic interests in the Muslim world.

Last night, President Bush reacted to the tape by calling the ideology and logic of al-Qaeda as "dark, dim, backwards".

At a press conference with the President of Colombia, Alvaro Uribe, Mr Bush said that Zawahiri's call for the US and the UK to withdraw from Iraq would not distract America from its mission in the Middle East.

"He’s saying, you know, leave," said Mr Bush, describing the video.

"As I have told the American people, the people like Zawahri have a ideology that is dark, dim, backwards," he said. "He’s threatening. They have come up against a nation that will defend itself."

"We will stay the course, we will complete the job in Iraq," said the President, who is under increasing pressure to demonstrate that America has a plan to withdraw from Iraq.

Twenty-eight US soldiers have been killed in the country in the last four days and a new Associated Press poll shows that public approval of President Bush's handling of the war has hit a new low.

America's approval of Mr Bush’s management of the war in Iraq, which has been hovering at a rate of just over 40 per cent for most of the year, has now dipped to 38 per cent.

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