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Young women are now three times more likely to become Islamist terrorists than they were seven years ago.

Although numbers are still small they rose from four per cent of those convicted between 1998 and 2010 to 11 per cent from 2011-15.

A 1,000-page analysis of 269 terror offences by the extremism think tank the Henry Jackson Society shows half of offenders came from highly deprived areas where the Muslim population is most segregated.

In Birmingham, three-quarters of offenders came from just two areas, Hall Green and Hodge Hill.

While in London, most offenders commonly came from Tower Hamlets, Newham and Waltham Forest. More than a third had been radicalised on the internet and one in 10 watched beheading videos.

Terrorists were also getting younger with an average age of 22, while 27 per cent lived at home with parents. The perils of being radicalised online were brought home by three London schoolgirls who fled the UK to join Islamic State in Syria in 2015.

(Image: Getty)

Shamima Begum, 15, Amira Abase, 15, and Kadiza Sultana, 16, went on to wed fanatics. Sultana was reportedy killed in an airstrike .

Report author Hannah Stuart said: “Family members are often the ones with prior concerns. They have a role in identifying offending behaviour.”

Security services have foiled 13 attacks in the past four years.

Britain’s counter-terror chief Mark Rowley said: “The spectrum involves one individual with a knife to groups of young men looking to get hold of firearms.”

He launched the ad campaign Action Counters Terrorism urging the public to be the eyes and ears of the security services.

Met Assistant Commissioner Rowley said there are 500 active investigations going on. He added: “We need the missing piece in the jigsaw in the investigations we are running that often the public have.”