Cameron warning on those who “quietly condone” IS

In the speech he said that the threat posed by the Islamic State group is “formidable and growing.”

“Only if we are clear about this threat and its causes can we tackle it. The cause is ideological. It is an Islamist extremist ideology, one that says the west is bad and democracy is wrong, that women are inferior and homosexuality is evil.

“It says religious doctrine trumps the rule of law and caliphate trumps nation state and it justifies violence in asserting itself and achieving its aims. The question is: How do people arrive at this world view?

“I am clear that one of the reasons is that there are people who hold some of these views who don’t go as far as advocating violence, but do buy into some of these prejudices, giving the extreme Islamist narrative weight and telling fellow Muslims ‘you are part of this’.

“This paves the way for young people to turn simmering prejudice into murderous intent. To go from listening to firebrand preachers online to boarding a plane to Istanbul and travelling onward to join the jihadis.”

This week Islamic State also said a 17-year-old British teenager blew himself up in northern Iraq. Talha Asmal from Dewsbury in West Yorkshire is believed to have become Britain’s youngest suicide bomber.

His family said he came “from a close-knit, hard-working, peace-loving and law-abiding British Muslim family” which unreservedly “condemns and abhors all acts of violence wherever perpetrated”. They said he had been exploited by extremists on the internet.

More recently three British sisters and their nine children disappeared after travelling to Saudi Arabia. Khadija Dawood, 30, Sugra Dawood, 34, and Zohra Dawood, 33, and their children, aged between three and 15 are still missing. The police have said that one of the sisters had made contact and that there was an “indication” that they may have crossed into Syria.

In a statement the women’s parents and other family members said: “We do not support the actions of the sisters leaving their husbands and families in the UK and of taking their children into a war zone where life is not safe to join any group.

“We plea (sic) to anyone thinking about making a similar journey not to go.”