Boris Johnson has demanded the advocacy group Cage "stop crying Islamophobia” and focus its "wrath" on Isis militants during a furious exchange with the organisation's research director over Jihadi John suspect Mohammed Emwazi.

Asim Qureshi rang Mr Johnson’s LBC weekly phone-in to challenge criticism he has received for saying Emwazi’s detention and treatment by British security services may have made him more susceptible to radicalisation.Mr Qureshi last week described Emwazi as an "extremely kind" and "gentle" man who had been harassed by MI5.

Mr Quareshi said Cage’s opinions over Emwazi had been “unfairly represented”, adding: “At the end of the day, what this young man has done is absolutely horrific”.

He continued: “As an organisation we have made a commitment against arbitrary detention, extrajudicial killings and torture, regardless of the perpetrator,” prompting fury from the Mayor.

Johnson said he was “moved to anger” over the thought that Mr Qureshi could lay blame for his radicalisation at the feet of MI5.

"I really, really think that the focus of your indignation and outrage should be on people who go out to join groups that throw gays off cliffs, that behead people who don't subscribe to their version of Islam, that glorify in the execution of innocent journalists and aid workers," he said.

"These should be the object of your wrath, not the security services who are trying to keep us safe.

"I urge you, I urge you more powerfully to differentiate between people like Mr Emwazi and ordinary Muslims and not somehow instantly to cry Islamophobia or whatever when people criticise, attack, denounce those who go out and engage in such atrocities. That should be your priority.” He suggested Mr Qureshi spend more attention on "the false understanding" Isis supporters have of Islam.

Mr Qureshi replied: "These things are extremely complicated. We never said that he was radicalised by MI5 to commit beheadings.