The family of Sheikh Omar Bakri Mohammad are applying for his asylum in the UK after claiming he had been tortured in Lebanon.
They say the radical preacher has suffered systematic torture while in custody at a maximum security prison.
The family say he should be allowed back into Britain on "humanitarian grounds" as his health has deteriorated and he is no longer able to walk.
The cleric caused outrage in the wake of the 2005 London bombings after saying he would not inform police if he knew Muslims were planning attacks.
He left the UK in 2005 and was told he would not be allowed to return.
But the cleric's son, Mohammad Bakri, told Sky News: "I'm here on the humanitarian basis. At the end of the day, many people find what he says distasteful, and he quotes things from the Islamic perspective.
"But I think unless you know the character, himself, like my father - I grew up with him - so therefore I understand the tactics that he uses to attract the media in order to pass the message of Islam.
"You may find that distasteful, but at the end of the day he has not committed any crimes in the UK."
Sky's Home Affairs Correspondent Mark White said the family's claims have not been independently verified.
"The families of Omar Bakri Mohammad say that he has been transferred to a maximum security prison ... in Lebanon," he said.
"They also say that he has been systematically tortured during his time in that maximum security prison.
"We have no independent verification of this, but the family insists that he is in very poor health.
"They claim that he is actually close to death and they're seeking an urgent appeal now to the UK authorities to have him returned to the UK under asylum."
Mohammad holds Syrian and Lebanese citizenship and lived in Britain for 20 years, where he headed the now-disbanded radical Islamist group al Muhajiroun.
He was among 54 people sentenced in Lebanon in November 2010 in trials of militants who fought deadly clashes with the Lebanese army in 2007.
He was convicted of belonging to an armed group that aimed to carry out terrorist acts and plots to kill Lebanese soldiers.
A Home Office spokesperson said: "An individual must be physically present in the UK in order to make a claim for asylum.
"Omar Bakri Mohammad was permanently excluded from the UK in 2005 on the grounds that his presence is not conducive to the public good.
"As Omar Bakri Mohammad is excluded from the UK, he will be unable to make a claim for asylum."
Conservative Party chairman Grant Shapps told Sky News: "People will have their own opinions, but there are proper processes in place to deal with these things."
Asked whether those processes meant that people had to be in the country to claim asylum, Mr Shapps added: "Those are the processes, that's right."