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.