Moazzam Begg
Former Guantanamo Bay prisoner Moazzam Begg started the advocacy group Cage after he was released without charge in 2005 Reuters

David Cameron may need to arm himself with a defamation lawyer after he singled out the controversial NGO Cage as an "extremist" organisation that supports jihad.

"This statement is simply false," said Cage spokesperson Lois Clifton. "Cage is currently seeking legal advice on whether David Cameron is guilty of defamation."

In a speech in Birmingham, in which he laid out government plans to tackle extremism, Cameron said:

"When you choose to ally yourselves with an organisation like Cage, which called Jihadi John a 'beautiful young man' and told people to 'support the jihad' in Iraq and Afghanistan it really does, in my opinion, shame your organisation".

The group, started by former Guantanamo Bay detainee Moazzam Begg, advocates for due process and adherence to law when dealing with those accused or suspected of terrorism.

Cameron's comments were directed at the National Union of Students (NUS) and their alleged connection with Cage.

Cage was roundly condemned in March, and lost its partnership with Amnesty International, when the group's research director, Asim Qureshi, referred to Mohammed Emwazi, popularly known as Jihadi John, who he met in 2011, as a "beautiful man... extremely kind, extremely gentle, extremely soft-spoken..."

Qureshi accused the police of playing a role in turning the 26 year old toward extremism.

Emwazi has been identified as the IS fighter who appears in the gruesome beheading execution videos of UK aid worker Alan Henning and journalists James Foley and Steven Sotloff.

"This description is clearly not in reference to an alleged killer of innocents including aid workers," said Clifton, noting Qureshi met Emwazi "before the Syrian conflict began and even well before the creation of Isis".

She characterised the government's criticism of Cage as hypocritical. "The government seems to be unwilling to look at their own actions and policy as contributing to radicalisation," she said.

"A report by the Home Office's Organisation for Security and Counter Terrorism documented three primary root causes of terrorism: first and foremost, grievances with British foreign policy; secondly, a perception of racism and Islamophobia toward Muslims in the UK; and thirdly, a profound sense of a lack of belonging to wider British society."

A request for comment from the Prime Minister's office referred back to Cameron's speech.

Other organisations, such as multi-faith group Faith Matters, have said that while it's a good starting point, the government's Prevent strategy to tackle the radicalisation of British Muslims "excludes and isolates groups that do not fit into its narrow definition of 'British values'".

"The oversimplification of the drivers towards radicalisation risk alienating swathes of British Muslims," said Fiyaz Mughal, director of Faith Matters. "Positing ideology as the main driver overlooks a multitude of factors that drives individuals towards violent extremism."

Faith Matters also criticised those on the other side of the issue who have built up "conspiracy theories" about Prevent that "corrode trust between the state and Muslim communities." Some have suggested the Prevent program is simply part of the government's intelligence agencies.

"Such smears, thrown at progressive organisations working in the field of Prevent, simply create a 'them and us,'" said Mughal, "fuelling a narrative that the government is somehow the real problem".

Clifton said that Cage continues to carry out work. "Part of this process is to try to understand in a dispassionate and evidence-based manner the trajectory of individuals who have engaged in acts of political violence," she said. "Cage has never supported terrorism in any way".