Boris Johnson is set to trigger a new controversy with an outspoken outburst - even by his standards - on the character and personality of jihadist bombers.
Citing an MI5 report into Muslim extremism, London's Mayor told The Sun newspaper: "If you look at all the psychological profiling about bombers, they typically will look at porn. They are literally w***ers. Severe onanists.
"They are tortured. They will be very badly adjusted in their relations with women, and that is a symptom of their feeling of being failures and that the world is against them.
"They are rejected by women, they are not making it with girls, and so they turn to other forms of spiritual comfort - which of course is no comfort."
He later told Sky News: "Certainly, the young men who get involved in this kind of thing do have a lot of problems in their lives.
"There's no question that they lack self-esteem and that they lack boundaries and that they feel like losers.
"We need to address it in all sorts of ways."
He added: "I don't think there's anything remotely controversial about what I have said."
It is not the first time Mr Johnson has launched an outspoken attack on jihadi terrorists.
Last year he said hoped the terrorist known as "Jihadi John" would be killed in a bomb attack.
In his Daily Telegraph column in August he said Britain must take on Islamic State (IS) and "try to close it down now".
Mr Johnson warned that doing nothing would mean a "tide of terror will eventually lap at our own front door".
But his inflammatory remarks in The Sun may reinforce the view of those Conservatives who believe Mr Johnson lacks the gravitas to be party leader and Prime Minister.
And Mr Johnson could also face accusations from radical Muslims and other ethnic groups of Islamophobia and racism.
The mayor, who is poised to return to the Commons in May in the safe Tory seat of Uxbridge and South Ruislip, told The Sun: "I fervently think we need to de-mystify this lot.
"The type of people who are likely to get involved in ISIS or get radicalised are the same sorts of people who are vulnerable to getting dragged into drug gangs or other types of criminal activity.
"They are just young men in desperate need of self-esteem who do not have a particular mission in life, who feel that they are losers and this thing makes them feel strong and feel like winners."
Mr Johnson backed the Muslim Cabinet minister Sajid Javid - seen by some Tory rivals as an opponent to the Mayor for the Conservative Party leadership - after the Culture Secretary said it was "absolutely right" to say Muslim communities carry a "special burden" to tackle terror.
The Mayor said: "I want to hear a proper angry Islamic theological denunciation of what is going wrong.
"We won't succeed if Western politicians just go around bashing and blaming Islam; that is hopeless.
"This problem can only be addressed if Muslim authorities and clerics find a powerful and compelling way of setting up an alternative narrative for young people that makes this seem irrelevant."
Pointing out his own great grandfather was a Turkish Muslim, the Mayor added: "I often hear voices from the Muslim intelligentsia who are very quick to accuse people of Islamophobia.
"But they are not explaining how it can be that this one religion seems to be leading people astray in so many cases.
"They are not being persuasive in the right way with these people. I am not yet hearing it in the way that we need to hear it."
But Mussurut Zia, general secretary of the Muslim Women's Network UK, branded the Mayor's comments as "irresponsible".
She told Sky News: "I feel they are going to lead to a greater divide.
"He has a responsibility to all his constituents, not just the readers' of The Sun."
Chris Doyle from the Council for Arab-British Understanding said: "He's using very agricultural language.
"It therefore risks trivialising and sensationalising very serious discussions and debates."
Speaking on a visit to Portsmouth, Chancellor George Osborne said Mr Johnson was known for his "colourful language".
He added the Mayor was "right not to be nice about these people".