Sheikh Sadik Al-Ghariani Photograph: Mahmud Turkia/AFP/Getty Images Source:  The Guardian

Chris Stephen and Josh Halliday, Aug. 29, 2014, Theguardian.com

Britain has been accused of housing a possible war crimes suspect after the Guardian learned that Libya's highest spiritual leader, the grand mufti Sheikh Sadik Al-Ghariani, helped orchestrate the Islamist takeover of Tripoli from the UK.

On a day when David Cameron announced tougher measures to tackle the threat from terrorists, the Foreign Office confirmed that Ghariani was residing in the UK, from where he is encouraging his followers to overthrow the Libyan government.

Earlier this week, the radical cleric celebrated the violent capture of Tripoli by Islamist militia force Libya Dawn and called for a widening of the rebellion using an online television channel registered by a close family relative in Exeter.

The day after Tripoli fell to the Islamist group Libya Dawn, Ghariani sent congratulations to the Islamist militants using his internet channel, Tanasuh: "I congratulate the revolutionaries in their victory, I give blessing to the martyrs," he said.

Ghariani's presence in Britain will prove acutely embarrassing for the government, emerging on the day the prime minister warned of a "greater and deeper threat to our security than we have known before" from Islamist extremists as the security threat level was raised from substantial to severe.

The matter is also likely to strain relations with Washington. American officials are understood to be furious that he has been allowed a pulpit to preach in the UK, particularly following his praise in June of the militant group Ansar Sharia, which the US blames for the killing of its ambassador Chris Stevens in Bengazi in 2012.