As details emerged about the identity of "Jihadi John", the masked Islamic State militant pictured in several hostage videos, questions started to arise about Cage, the advocacy group that had been in close contact with the man now known to be called Mohammed Emwazi between 2009 and 2012.
Cage has caused controversy by suggesting that MI5 harassment could have contributed to the radicalisation of the Kuwaiti-born computer graduate who grew up in west London.
Human rights groups say they are doing "vital work" but critics have called the organisation "apologists for terror".
Cage describes itself as "an independent organisation working to empower communities impacted by the War on Terror" and has spoken out against the UK's anti-terrorism laws.
Cage said Mohammed Emwazi had sought their assistance after being interrogated by a British security official in the Netherlands following an attempted visit to Tanzania.
Prime Minister David Cameron has defended the security services amid criticism that they failed to stop Mohammed Emwazi from leaving the UK for Syria.
London Mayor Boris Johnson said accusations that the security services were at fault were "incredible".
He said: "It is beyond satire and amounts to nothing less than an apology for terror".
Lord Carlile, the former independent reviewer of terror legislation for the government, said: "At the very least Cage are guilty of sloppy thinking and very unwise language.
"Before they can command any credibility from the wider community, they should make it clear that they reject the murder by ISIL of Christians and of Muslims who disagree with their views, and that they reject beheading and burning people alive.
"They should also give clear advice that joining ISIL constitutes a criminal act."
'Hypocrisy ferments extremism'
But the human rights lawyer Clive Stafford Smith defended the "vital" work of Cage and denied they are apologists for terrorism.
He said: "They do important work and the UK authorities need to understand that alienating moderate Muslims is the worst thing that could possibly be done at this time.
"I myself represent those said to be 'terrorists' and since Magna Carta, in 1215, we have presumed people innocent rather than guilty.
"If criticism must be levelled, it should be aimed at those who betray the fundamentals of our legal system by locking people up without trials, or just assassinating people with drones.
"Of the people who they said were the worst of the worst terrorists in the world, we have thus far demonstrated that at least 750 out of 779 were not - and that is a 96% error rate by the CIA and others.
"While I do not know enough about the individual cases of Mohammed Emwazi and Michael Adebolajo and their radicalisation, it is clear beyond dispute that when we jettison our principles we make ourselves hypocrites and hypocrisy is the yeast that ferments extremism."
What is Cage?
Cage, formerly known as Cageprisoners, was set up in London in 2004, and has just four full-time employees.
Moazzem Begg joined the group when he was released from Guantanamo in 2005 and is still the outreach director of the organisation.
In February last year Mr Begg was arrested and held at Belmarsh prison on terrorism charges relating to the civil war in Syria.
He was released after seven months, when all charges were dropped.
Cage told the BBC that in the past they had been funded by the Joseph Rowntree Charitable Trust and the Roddick Foundation.
However, Cage said their bank accounts were frozen last year, at the time of Mr Begg's arrest.
Although he was cleared of all criminal charges, the organisation's accounts have not been reinstated and Cage say they now rely on community support.
The Charity Commission told the BBC: "We have compliance cases open into both the Joseph Rowntree Charitable Trust and the Roddick Foundation.
"In both cases the Commission's regularity concerns are about how the trustees have ensured that charitable grants made to non-charitable bodies are only used for exclusively charitable purposes in line with their objectives.
"This regulatory engagement has included robustly examining each charity's decisions to previously make grants to Cage, which is not a charity.
"Public statements made in the last few days by Cage raise clear questions for a charity considering funding its activities as to how they could comply with their legal duties as charity trustees."
- The family of Michael Adebolajo, who was convicted of killing Fusilier Lee Rigby in Woolwich in May 2013. Cage's research director, Asim Qureshi, said that Michael Adebolajo, had been harassed by the security services prior to his violent action
- Cage campaigned for the release of the Salford taxi driver Alan Henning, before he was murdered by Islamic State militants in Syria last October
- Dr Aafia Siddiqui who is serving an 86-year jail term for the attempted murder of an FBI agent in disputed circumstances. Her family in Pakistan has said she is innocent but US prosecutors described her as an al-Qaeda sympathiser
- Anwar al-Awlaki, an American-born cleric of Yemeni descent, who was a key figure in al-Qaeda in the Arabian Peninsula (AQAP). It is understood he was killed in an American drone attack in Yemen in 2011
- Shaker Aamer, a British resident but originally from Saudi Arabia, who has spent 12 years at Guantanamo.
Following the naming of Mohammed Emwazi, Cerie Bullivant, press officer at Cage, said: "There is going to be pressure on Muslims to condemn and apologise, but we must remember we are humans like every one else.
"We feel the same shock and terror when we see these sights on TV, whether it is barrel bombs or beheadings.
"We should not have to justify our humanity by running out and feeding into this idea that all Muslims are culpable for the actions of one person."