Anjem Choudary says he understands that the Islamic protesters who this week greeted British troops returning from Iraq with placards calling them "murderers" and "butchers" are not helping to improve community relations.

"I can see that the British public will regard the protesters as insensitive," he says, smiling. "But in my opinion, that is outweighed by our sensitivities to families in Iraq who've lost relatives at the hands of the British. The troops were not heroes, but cowards, doing the bidding of a British government engaged in state-sponsored terrorism."

Speaking exclusively to the Evening Standard in an East London coffee shop that has been cleared of other customers ahead of our arrival - a 6ft 4in minder sits off to the side - the British-born Muslim extremist crudely likens the home-coming troops of the 2nd Battalion Royal Anglian Regiment to "Nazis".

"Those British troops are guilty of torture and atrocities in Iraq and we Muslims will not swallow the argument that as soldiers, they were just following orders."

Choudary, who offers no proof to back up his claims, is a lawyer by training. While almost all the other high-profile "preachers of hate" find themselves imprisoned or deported, Choudary, 41, enjoys freedom in the UK, despite the fact that he has helped found two jihadist Islamist groups - Al Muhajiroun and Al-Ghurabaa - both since banned for "glorification of terrorism".

His fanatical views have made him possibly the most reviled man in Britain, but he is unrepentant.

"That's a badge I would wear with pride," he says. "It's inevitable that when you offer an alternative morality and way of life, many people will hate you for it." He characterises Britons - "with their alcohol, gambling, prostitution and pornography" - as "living like animals in a jungle".

But if he hates the British way of life, why stay? "There are parts of the lifestyle, such as fish and chips, I like very much," he quips. "For the rest," he shakes his head. "But I was born in this country, I was educated here, I have every right to stay."

He refuses, though, to see any hypocrisy in the fact that his East London-based family - he is separated from his wife, Rubana Akhtar, with whom he has three young children, aged 13, nine and three - live on benefits of allegedly £25,000 a year, funded by the taxpayers he despises.

He does not deny that he receives benefits (he won't confirm how much), or that he uses the NHS, or that his children attend state-funded faith schools, but he bristles at my proposition that taking handouts compromises his position.

"I don't think it's of any importance," he says. "People think that those who live off benefits are in some way criminal or less intelligent. It's a way of vilifying me, but it's irrelevant to my ideological views and to what I do."

Another subject Choudary is sensitive about is reference to his undergraduate days at Southampton University where he was known as "Andy" and earned a reputation as a womaniser into "cider, casual sex, cannabis and LSD".

Although fellow students who say they took drugs with him have come forward to substantiate these claims and to remark that "he didn't seem very religious at the time", Choudary insists the story is "a fabrication" peddled by his enemies to discredit him.

The son of a market stall holder of Pakistani descent in Welling, south-east London, Choudary was nevertheless a secular Muslim who became radicalised only when, after qualifying as a solicitor, he met firebrand preacher Sheikh Omar Bakri Mohammed at a mosque in Woolwich.

Later, Choudary became his right-hand man in the post 9/11 formation of Al-Muhajiroun, but with Bakri exiled in Lebanon since 2005 after vowing that Muslims would "give the West a 9/11 day after day", Choudary became the Islamists' militant spokesman in the UK.

These days, Choudary is associated with the radical website Islam For the UK and the fundamentalist sect Ahlus Sunnah wal Jamaah, a secretive group founded in London in 2005 as a successor to Al-Muhajiroun.

They claim up to 1,000 members, and it was the Luton branch of this sect, admits Choudary, who organised the anti-troops demonstrations this week.

Their ultimate aim, he says, is "to fly the flag of Allah above 10 Downing Street" and bring about - "through jihad" - "a pure Islamic State with Sharia law in Britain".

Asked what the system of Sharia would mean for westerners living in England, Choudary, who no longer practises conventional law and is now a judge in the Sharia Court of the UK, says: "Every woman, whether Muslim or non-Muslim, would have to wear a traditional burkha and cover everything apart from her face and hands in public. There is a view that women would also wear the niqab [full face veil], but only in certain circumstances.

"In matters to do with the judicial system and the penal code, one male witness is sufficient to counter the testimony of two females. Also, anyone one becomes intoxicated by alcohol would be given 40 lashes in public. And people who commit adultery would be stoned to death."

The fact that no pure Islamic state exists outside Saudi Arabia, and that it's unlikely to win many converts in Britain, does not deter Choudary. But the mechanism for turning our liberal democracy into a regressive Islamic state is a trickier subject to broach.

Such a revolution can only come about through "jihad", Choudary admits. There are two types: jihad of the sword, and jihad of the word. "I am engaged in jihad of the word," he states.

But that could entail inciting people to violence: is he guilty of inspiring the next generation of suicide bombers?

Only last month, British Army officers in Afghanistan complained they were engaged in "a surreal mini civil war" with homegrown jihadists "bizarrely sporting British accents who'd travelled there to support the Taliban.

Has he ever had young Muslims come to him and say they want to leave Britain to do jihad against our troops abroad?

"You know," he says, looking me in the eye, "there are some things one can't discuss. If it were true that people came to me, it would not be wise for me to tell you. But let me say this: what I say publicly is what I say privately. If they ask about doing jihad in this country, I tell them they live here under a covenant of security and that they are not allowed to kill people or target their wealth."

If Choudary is being on the level, you'd logically expect him to condemn, outright, the home-grown terrorist attacks of 7 July 2005 on London, yet invited to do just that, he refuses.

"I'm not in the business of condemning or condoning them," he says. "If I condone them, you will say I am supporting terrorists and glorifying terrorism. But if I condemn it, tha t'll give the green light [for British troops] to do whatever they want abroad without thinking there'll be repercussions in this country.

"Rather I think what we should do is look at the root causes of 7/7, like the bombing by the British and the Americans of Afghanistan and Iraq."

But what does he say to those who want to leave to do jihad abroad? Does he fire them up or deter them? "If your family is subject to terrorism by Britain, I think it's natural you'd want to go help them," he says. "But now you're asking me questions which you know, and I know, are contrary to the glorification of terrorism [laws] and inciting people to acts of terrorism, and I'm not going to be entrapped."

But it's only a trap if he encourages them to go. All Choudary has to say is that he doesn't, wouldn't. But he won't.

I remind him of inflammatory comments he'd made four months ago at a public meeting in Newham when he said: "There are three types of Muslims: those in prison, those of us on our way [to prison], and non-practising Muslims."

Which one is he? "I live under the expectation that I could be taken to prison at any time. We have an absurd kangaroo legal system in this country. The sooner we overthrow it and implement Sharia, the better."

Does he model himself on Osama bin Laden? "I am an ordinary Muslim but let me tell you something: Sheikh Osama bin Laden is more popular in the Muslim world than any leader in charge. If there were elections in countries across the Muslim world today, he would win every one of them."

How would he like to be remembered? As a terrorist or a man of peace? "If terrorism is calling for the Sharia, supporting the innocent civilians being tortured and abused abroad, then yes, I'm the biggest terrorist in the world. But if by terrorism you mean the use of violence for political ends and not caring about the lives of ordinary people, then the biggest terrorists in the world are Gordon Brown and George Bush."

Our time is almost up, but I test his sense of humour with one last question: does he ever bump into anyone from his Southampton days who still remembers him as Andy? His face clouds over. "Turn off your tape recorder," he demands, "I'm ending the interview here and now."

Suddenly his minder is towering over me. "If you don't turn that off, I will take it off you and you'll never see it again," he says menacingly. And with that Choudary stands abruptly and makes some bizarre derogatory comment about me probably being a paedophile. The veneer of gentility shattered, he strides out of the café without so much as a backward glance.

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