At least 10,000 women and children are at risk of being murdered or seriously injured in cases of domestic violence by partners or former partners, police figures show.
Police assessments from 33 of the 44 forces in England, Wales and Scotland obtained by the Guardian revealed that 10,952 people, mainly women, were categorised as being at high risk of facing a violent death in the home or of suffering severe violence, in the year to November.
The newspaper said that as domestic violence is widely under-reported the true figure is likely to be higher, and claimed that numbers could be further skewed by police forces gathering and collating information in different ways.
Officers who assess the potential risk to victims at domestic violence incidents largely use a national protocol called Dash - domestic abuse, stalking and honour-based violence - the Guardian said, but some forces still use their own assessments or the judgment of officers at the scene.
The figures showed that in Sussex 211 women were at high risk of being murdered or suffering serious harm from former partners on August 31 last year, while 17 individuals in Surrey were at high risk in November 2013.
West Midlands assessed 2,082 individuals as high risk over 12 months, but the force said this would be the minimum number as four police units had failed to maintain records.
In Essex some 1,801 women and children were identified as being at high risk of harm in the year to November 2013, while in the Metropolitan Police area just 87 women and children were assessed as being at high risk in one month.
Sandra Horley, chief executive of domestic violence support charity Refuge, said women and children at the highest risk should receive proper protection and that police should not regard assessment as a "tick box" exercise.
She told the Guardian: "There is no point in doing a risk assessment if the knowledge gained does not lead to proactive safety planning measures that keep women and children safe from violent men.
"I am deeply concerned that in too many cases this does not happen."
The newspaper claimed that some forces, including Cambridgeshire, Durham, Humberside and Lancashire, were unable to provide risk assessment records for any one time because it would involve too much searching of records, an admission which drew criticism from Laura Richards, a criminal behavioural analyst who developed the Dash assessment.
She said: "The fact that a force cannot grab those individuals from their data quickly means there is clearly a problem. You get to the perpetrator through the victim. The victims know the perpetrators best, they tell us about the behaviour of high risk perpetrators."
Dash provides national standards for identifying women and children at the highest risk of domestic violence so police and agencies can intervene.
Assistant chief constable Louisa Rolfe, spokeswoman for the Association of Chief Police Officers on domestic violence, told the Guardian it was critical for officers to understand risk so they could protect potential victims.
She said: "While forces may capture this information in different ways I am working with forces and the College of Policing to ensure a consistent and positive police response for every victim, focused upon ensuring their safety."