Omar Bakri Mohammed, who has lived in Britain for 20 years, left the country on Saturday for Lebanon.
British authorities, who have monitored the cleric's radical activities for years, acted swiftly to block his return.
Home Secretary Charles Clarke revoked Bakri’s indefinite leave to remain in Britain "on the grounds that his presence is not conducive to the public good".
Mr Clarke has wide-ranging powers to exclude people from the country if they threaten national security.
The cleric, who headed the now defunct militant Islamic group al-Muhajiroun, has three months to call for a judicial review of the decision.
Bakri's close associate, Anjem Choudary, told The Associated Press the cleric would not challenge the move - but neither would he be silenced.
"With the internet and other means, we can still hear from him wherever he is preaching," Mr Choudary said.
Police say Bakri tried to recruit British Muslims for jihad, or holy war, in Afghanistan, Chechnya and conflicts involving Muslims around the world.
He was briefly detained in Beirut but released after being questioned about the circumstances of his entry into Lebanon.
Meanwhile, Jordan said it wanted to extradite another firebrand cleric, Abu Qatada, who is among 10 foreigners detained in Britain and now facing deportation.
Jordanian authorities convicted him in absentia in 1998 and again in 2000 for involvement in a series of explosions and terror plots.
Britain had long monitored Abu Qatada's activities and had him in custody or under house arrest since 2002.
Until now Britain was unable to deport him to Jordan because as a signatory to the European Convention on Human Rights it cannot send people to countries where they may face torture.
But the British government signed a memorandum of understanding with Jordan on Wednesday guaranteeing deportees would be treated humanely.
Britain is working on similar agreements with nine other countries, including Algeria - the home country of the nine other men in custody.