The new “exclusion order” will allow Charles Clarke, the Home Secretary, to prevent any attempt by the leader of the al-Muhajiroun group to re-enter Britain after he fled to Lebanon at the weekend.

John Prescott, the Deputy Prime Minister, admitted yesterday that he had no power to deal with the cleric, who reportedly described the July 7 bombers as “the fantastic four”. Mr Prescott said: “At the moment he has the right to come in and out. That is the circumstances at present and we have to change situations in this country by law. It’s a democracy, not a dictatorship, for God’s sake.”

He made clear his dislike of Sheikh Bakri Mohammed, who claims to have gone to Beirut on a family visit, saying: “I just say, enjoy your holiday — make it a long one.”

The Syrian-born cleric, 47, who flew to Lebanon the day after Tony Blair gave warning of a crackdown on the “preachers of hate”, boasted yesterday that he intended to challenge the new rules by coming back next month.

“If someone is accusing me of committing a crime I will come back to clear my name,” he told The Times. “I have done nothing wrong. No one can stop me returning to London.”

Whitehall officials believe that they can. Revised immigration rules could be introduced within nine days and do not need parliamentary approval. Mr Clarke will be given new powers to exclude extremists on the grounds that they foster hatred that may lead to intra-community violence and express views conflicting with Britain’s culture of tolerance.

A two-week consultation paper issued last Friday paves the way for giving the Government more reasons to exclude people whose presence in Britain they assess to be “not conducive to the public good”. Officials in Whitehall believe that the existing grounds are not wide enough to ban Sheikh Bakri Mohammed. If he comes back before the rules are introduced he could be deported but that would involve a court process that could take years. Exclusion means he would be stopped at the airport and put on a plane to Lebanon.

Diplomats in the region were questioning whether Whitehall had made it possible for Sheikh Bakri Mohammed to escape to Lebanon as a haven from possible prosecution in Britain. When Mr Blair announced his 12-point plan to tackle extremists, he revealed that he had been having talks with Lebanese leaders about taking deported militants.

The Home Office insisted last night it had done no deal with Sheikh Bakri Mohammed to allow him to quit Britain rather than face charges.

The Lebanese Interior Ministry also rejected suggestions of a deal, saying: “He arrived on a valid Lebanese passport. Everything is normal with him.”

His mother lives in a poor Sunni Muslim district in Beirut where many neighbours supported the sheikh’s radical views. To avoid the media attention yesterday he moved to a family home in a mountain village where his mother stays to escape the heat of summer.

At his home in Edmonton, North London, his wife said that she did not know when her husband was returning or if she and their seven children would join him in Lebanon.

As the sheikh has been given “indefinite leave to remain” he can stay away for up to two years. If he remains abroad for longer he loses the status. An exclusion order is reviewable after three years so if one is imposed his status will end as he will have been out of the country for more than two years. Bakri could challenge an exclusion order in the courts, though only from outside Britain.

Lord Falconer of Thoroton, the Lord Chancellor, last night dismissed the idea that the sheikh and other radical clerics could be charged with treason. He also ruled out holding secret trials without juries.

• Judges have been drawn into areas of political controversy in the fight against terrorism “through no fault of their own”, Michael Howard, the Conservative leader, said last night. He blamed the Government’s introduction of the Human Rights Act, but warned judges that “aggressive judicial activism” could compromise security.

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