More than a third of suspected extremists referred to the government anti-radicalisation programme Prevent had experience of domestic violence, research suggests.
Police said of 3,045 people referred to the scheme in 2019, 1,076 had a link to domestic abuse as an offender, victim or witness.
The cases ranged from witnessing violence in the home as a child, to one man who had a conviction for attempted murder.
The research, called Project Starlight, found that 15.4% of Prevent referrals were victims, nearly three times the estimate for the general population.
National co-ordinator for Prevent, Detective Chief Superintendent Vicky Washington said: “This initial research has resulted in some statistically significant data which cannot, and should not, be ignored.
“Project Starlight has indicated a clear overrepresentation of domestic abuse experiences in the lives of those who are referred to us for safeguarding and support.
“It is absolutely vital that we use this information to shape what we do, and strengthen our response across all of policing, not just in counter terrorism.”
The research found that among the cases with a domestic abuse background, 28% of referrals were linked to Islamist extremism, while extreme right-wing ideologies accounted for 18%.
A third category, cases where there was no fixed ideology, accounted for 21%.
The link between children who witness domestic abuse and violent crime in later life has long been recognised, and counter-terrorism police now plan more research into its connection with extremism.
Det Chief Supt Washington added: “It is more important than ever that we look beyond traditional boundaries of what we do, and work towards understanding the bigger picture.
“This research is not about stigmatising anyone or claiming that one factor necessarily links to another, it’s about us doing all we can to strengthen our understanding and approach, to ensure the right support is in place.
“And it’s about a joint mission to protect vulnerable people from all forms of harm.”