More than two-thirds of Islamism-related terrorism offences or suicide attacks in the UK over the last 10 years were perpetrated by British citizens, according to a report published.

Some 69% of such incidents from 1999 to 2009 were carried out by Britons, the study by think-tank The Centre for Social Cohesion found.

Almost half (46%) were committed by individuals of a south central Asian ancestry, while the second and third most frequent regions of origin were eastern Africa (16%) and northern Africa (13%).

Some 48% of the 127 Islamism-related terrorism offences or suicide attacks, collectively referred to as Islamism related offences (IROs), were committed by individuals living in London, the report found.

The next two most common regions were the West Midlands (13%) and Yorkshire and the Humber (9%).

Nearly a third of individuals who committed IROs (32%) had a direct link to one or more proscribed organisations, the two most prevalent being al-Muhajiroun (15%) and al Qaida (14.5%), the report found.

Seven of the UK’s eight major bomb plot cells contained individual members with direct links to al Qaida - only the failed London bombers of July 21 2005 lacked undisputed evidence of direct contact with any proscribed organisation.

Just under a third (31%) of all individuals who committed IROs attended one or more terrorist training camps, the most common location being Pakistan. Seven of the eight major bomb plot cells contained members who attended terrorist training camps.

More than two-thirds (68%) of IROs were committed by those aged below 30.

The most common status was unemployed (35%) - but 42% were perpetrated by individuals either in employment (32%) or full-time education (10%).

The report concludes: “Al Qaida and al Qaida-inspired terrorism remains the biggest threat to the UK’s national security.

”The Security Service estimates that over 2,000 people in the UK pose a terrorist threat and in March 2005 it was estimated that there were up to 200 al Qaida-trained operatives in the UK.

”The British-based threat does not only affect the UK: a number of British Muslims have been convicted in foreign courts or have fought for (or trained with) terrorist or extremist Islamist groups abroad.”