Muhammad al-Massari, the Saudi dissident, said that if Charles Clarke, the Home Secretary, tried to target him as the first to be deported, he would wreck the initiative in the courts. “He wants to look tough by picking high-profile people, but I am ready to fight him in the courts,” he said.

Another hardliner believed to be on the government list, Yasser al-Siri, an Egyptian-born website operator, said: “I’m not worried about expulsion. My legal team think it’s impossible.”

Mr Clarke said he expected to see the first of the extremists excluded from Britain in the coming week.

Dr al-Massari, 58, who has lived in Britain since 1994, has been condemned by MPs from all parties for reportedly backing the killing of Tony Blair on his website and radio station.

As police and immigration officials draw up plans to seize foreign extremists early next week, lawyers and Muslim groups predicted that the attempted deportations would almost certainly end in chaos. Senior figures inside Whitehall are worried that despite the warning by Tony Blair that “the rules have changed” it will not prevent human rights lawyers derailing the Government’s pledge to begin deportations within days.

One source said: “The law hasn’t changed, nor the deportees’ right of appeal, so no one is sure how we cut the time it takes to put these people on a plane out of the UK. It certainly can’t be done within days.”

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