A link between terrorism plots and hardcore child pornography is becoming clear after a string of police raids in Britain and across the Continent, an investigation by The Times has discovered. Images of child abuse have been found during Scotland Yard antiterrorism swoops and in big inquiries in Italy and Spain.

Secret coded messages are being embedded into child pornographic images, and paedophile websites are being exploited as a secure way of passing information between terrorists.

British security services are also aware of the trend and believe that it requires further investigation to improve understanding of terrorists’ methods and mindsets. Concerns within the Metropolitan Police led to a plan to run a pilot research project exploring the nature of the link. One source familiar with the proposal said that this could eventually lead to the training of child welfare experts to identify signs of terrorist involvement as they monitor pornographic sites.

Concerns have already been expressed at Cabinet minister level about the risk of vulnerable Muslim youths being exploited by older men.

Officers have noted that child sex abuse images have been found during investigations into some of the most advanced suspected plots. However, it is understood that the proposed research project was never implemented because the AntiTerrorism Branch was overwhelmed by the sheer number of cases it was having to deal with.

It is not clear whether the terrorists were more interested in the material for personal gratification or were drawn to child porn networks as a secure means of sending messages. In one case fewer than a dozen images were found; in another, 40,000.

British security sources confirmed that such a link had been discovered in several cases. They noted the contradiction between people supposedly devoted to theocracy and Islamic fundamentalism and their use of child pornography. “It shows that these people are very confused,” a source said. “Here they are hating Western decadence but actually making use of it and finding that they enjoy this stuff.”

Baroness Neville-Jones, Conservative security spokeswoman and former chairwoman of the Joint Intelligence Committee, said: “The information about a possible link between extremism and child pornography potentially provides useful insight into three things: the methods that extremists use to communicate; the methods they use to target vulnerable people in society; and the techniques they seek to use to conceal their online activities.” She added: “There is no doubt that these possible linkages should merit further research.”

Andrew Dismore, the Labour MP and chairman of the parliamentary Joint Committee on Human Rights, said: “This is an important development. We have to do more than just the police work. It needs child protection, criminological and psychological work. It could become a very important weapon in the fight against terrorism.” He urged researchers to review cases where terrorists had been convicted to look for this link.

The first British suspicions of a link between child sex abuse and jihadis emerged in London in 2006 when antiterrorism police in two unrelated investigations were shocked to find computerised images of hardcore child pornography. The key case that tipped off the security services to a plausible link involved the “White-chapel Rapist”, Abdul Makim Khalisadar. A former Mujahidin and a preacher at the East London Mosque, he was being examined for his links to a hardcore Islamic militant who was later convicted of terrorism. Khalisadar was never convicted of terrorist offences. The other investigation involved a young religiously observant Muslim.

The Times has learnt that a criminal investigation also found child pornography on computers after a raid in 2001 at a mosque run by an al-Qaeda recruiter in Milan. Italian police believe that the images were encoded with messages. At a forthcoming terrorism trial in Spain, the alleged mastermind of a Muslim cell has also been accused of downloading hundreds of child sex abuse pictures and videos.

Meanwhile, police uncovered a right-wing terrorist plot when they raided a home after being tipped off about pornographic images. This June, the Nazi sympathiser Martyn Gilleard was jailed for 16 years after being found guilty of terrorism. Police found 39,000 indecent images of children at his flat in Yorkshire.

Invisible ink for the internet age

— Messages may be concealed within digital images and audio, video or other files. The method is called steganography, derived from the Greek for “covered writing”

— Although the average person will not be able to detect the hidden messages by either listening to or viewing a file, the intended recipients can use applications to reverse the steganography process and gain access to the information

— Experts say that the advancement in encryption technology is outpacing the authorities’ abilities to monitor suspected terrorists and paedophiles

— Italian authorities uncovered files of child abuse images that had been manipulated by a terrorist cell after a raid on the Via Quaranta mosque in Milan in November 2001. Investigators claimed that the terrorist cell encoded the images before sending them to each other

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