My Gold Music : Islamic Scholar Issues Anti-Terrorism Fatwa
Muhammad Tahir ul Qadri is a leading figure who has promoted peace and interfaith dialogue for 30 years.
He said he felt compelled to issue the fatwa because of concerns about the radicalisation of British Muslims at university campuses and because there had been a lack of condemnation of extremism by Muslim clerics and scholars.
Ul Qadri says his fatwa, which is aimed at persuading young Muslims to turn their backs on extremism, goes further than any previous denunciation.
"This is the first, most comprehensive fatwa on the subject of terrorism ever written," said ul Qadri, who has written about 350 books on Islamic scholarship.
He is a scholar of Sufism, a long tradition within Islam which is widely seen as focusing on peace, tolerance and moderation.
Nigerian Umar Farouk Abdul Mutallab, accused of trying to bomb a US-bound plane on Christmas Day, studied at a London university until 2008.
Government officials in Yemen, where Mutallab began his journey, have said he was radicalised while in Britain.
However, the British Government claims his introduction to hardcore extremists happened after he left the UK.
Government officials will be among those joining ul Qadri for the launch of the fatwa in central London.
The Muslim Council of Britain, an umbrella organisation representing some 500 Islamic groups, has welcomed the fatwa.
Ul Qadri will tell his audience: "The reality is that whatever these terrorists are doing it is not martyrdom. All these activities are taking them to hellfire."
The 59-year-old was born in Pakistan and is head of the global Minhaj ul Quran religious and educational organisation which spreads his Sufi ideas.
A former Pakistani minister and associate of assassinated prime minister Benazir Bhutto, he delivers lectures worldwide promoting his message of harmony and was one of the first Muslim leaders to condemn the 9/11 attacks in the US.
While ul Qadri has followers around the globe, it is in Pakistan where he has millions of followers and in the diaspora that his impact is likely to be greatest.
Britain has about 1.7 million Muslims, mainly of Pakistani descent.
The UK's security services say nearly all major terrorism plots since 2001, including the 2005 London bombings which killed 52 people, have been linked to Pakistan.
Ul Qadri said he is confident his edict will have a significant impact because he has drawn on classical teachings and authorities acceptable to all sects of Islam.
"I will say more than 50% will change their way, they will be influenced," he said.
"Of the remaining 50% at least some of them, half of them, will become doubtful about their life, their terrorist activity," he said.
Tim Winter, a lecturer in Islamic studies at Cambridge University, said while there had been similar fatwas in the past, ul Qadri did appear to have gone further than most.
"To declare the miscreants as unbelievers is unusual because it is not really clear that the rules allow one simply to say that they are not Muslims."
He added: "Those who are already hardliners will pay no attention at all but 'swing voters' - poorly-educated and angry Muslims who respect mainstream scholars - will probably take note.
"Certainly it is a helpful initiative."
Ul Qadri's pronouncement will be welcomed by authorities in the UK and by other Western governments seeking to stamp out extremism - but the respected scholar said their backing is irrelevant to his views.