I thought Britain was a free and civilised country where I would no longer hear talk of public executions - I used to live in Saudi Arabia, where weekly, public beheadings are the norm. I was wrong. There is an unchallenged, unreported Islamist underworld in the UK in which talk of jihad, bombings, stabbings, killings and executions is usual. Rhetoric is an indication of a certain mindset and, I believe, the prelude to terror.

In my book, The Islamist, I try to reclaim Islam from Islamism and separate the ancient spiritual path from a post-colonial political ideology. Condemnation of the book, mainly by Islamists, has not ceased for over a month.

In Manchester in April, Hassan Butt, a one-time jihadist who is now opposed to extremism, was stabbed and beaten for speaking out against fanaticism. He now lives in hiding. Why was this not reported in the mainstream media?

The Islamist underworld is assisted greatly by cyberspace - from Baghdad to Birmingham, Islamists and their jihadist twin brothers exchange information and coded messages on the web. Before Hassan's stabbing, his interview with an American media outlet condemning terrorism had been circulated on the web.

In internet chatrooms and discussion threads the Islamists break news of beheadings in Iraq, the downing of US helicopters and discuss who is next on their agenda of killing and destruction. The mainstream media is bewilderingly unaware of this fast-moving, influential underworld.

But things took an uglier turn recently. Showkat Ali, a member of Hizb ut-Tahrir, who is training in Birmingham to become a schoolteacher, wrote a rap-like poem and posted it on several prominent Muslim websites. He wrote that his poem "was inspired by several Muslims who have betrayed Islam and the Ummah and are now openly working for the Crusader West in its losing battle against Political Islam". Purporting to speak my mind and likening me to Judas, he wrote:

No ifs no Butts [Hassan Butt]
Some people after me
To stab me in the heart
Like they did Hassan in Manchester

I dread the return of the Caliphate
Who will apply to extradite me
Put me on trial
And then execute me
As a traitor.

I believe the above lines are a coded call for my death, written in the first-person narrative to absolve Ali and his organisation from any responsibility.

I was once involved with Hizb ut-Tahrir and know from first hand the games it plays. The Hizb raise the political temperature, manipulate violent rhetoric and then create the climate for others to pull the trigger. I saw this happen on my college campus in Newham in 1995, when Ayotunde Obunabi was killed as a result of the supremacist, jihadist, racist milieu the Hizb fostered on campus. Soon, on a larger scale, the Hizb gave birth to al-Muhajiroun, whose members and associates bombed Tel Aviv in 2003, London in 2005 and plan other atrocities that the security services continue to monitor. How much longer will we tolerate the rhetoric of jihadism in our midst?

In my experiences of living in Saudi Arabia in the aftermath of the 2004 and 2005 terrorist attacks in Riyadh and Jeddah, the most powerful weapon against Islamists and jihadists is to create public spaces in which former extremists can discuss why they entered Islamist networks and why they left. This removes the impenetrable mystique of these networks. It opens up their underworld. On Saudi television, former Islamists and jihadists recounted in detail why they abandoned the jihadist wing of Wahhabism, or al-Qaeda.

This scrutiny of extremism gives the public a better understanding of radicalisation, terror and its ideological underpinnings. More importantly, it gives people hope that we can together defeat this cancer in our midst. It also prevents a new generation of young Muslims from trying to walk the path that I traversed.

When courageous young men like Butt are stabbed and the media and authorities remain silent, it gives the wrong signal to those inside extremist organisations who are considering leaving. The rhetoric of "betrayal" also silences moderate Muslims who fear reprisals for speaking out, one reason that Muslim condemnation of extremism in Britain has been relatively low key. When coded death threats appear on popular Muslim websites, it prevents the emergence of a robust public space in which former Islamists can demolish the psychological confidence of extremists. To speak out against Islamism is not betrayal, it is fidelity to Islam and humanity. In the Quran, God refers to ennobling bani adam, or humanity. Ours is not a tribal religion. To condemn and dissociate from Islamism in all its forms is a religious duty, as illustrated by the words and actions of the majority of the world's Muslim scholars, from al-Azhar in Egypt to Deoband in India.

In Britain, the differences between Islamism and Islam have been blurred to the extent that many Muslims fail to draw the distinction, as do large numbers of us on the left. Mistakenly, we sympathise with those who articulate anti-American, anti-war, pro-Palestinian grievances, without realising that Islamists of the entryist school are not allies of the left, but sworn enemies with a long history of terrorism against leftists in, among other countries, Algeria, Palestine and Bangladesh. We should know our Muslim from our Islamist. Just as we don't talk to the BNP to understand white, working-class grievances, we need not engage with Islamists to comprehend Muslim suffering.

Islam, with its history of plurality and spirituality, has a natural home in Britain. Islamism, a political ideology set up to confront the west, does not. Today, it is talk of execution of moderate Muslims; unless we stem the rising tide of radical Islamist rhetoric in Britain, a prelude to jihadism, then the carnage of Baghdad may well erupt in Bradford and Birmingham.

Ed Husain is author of "The Islamist", published by Penguin

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