I've posted the CPS definition of DV taken from here. As I read it, emotional abuse is already prosecuted (although I might be wrong).
www.cps.gov.uk/publications/prosecution/domestic/domv_guidance.html#a02
The explanatory text says more.
The Government definition of domestic violence is:
"any incident of threatening behaviour, violence or abuse (psychological, physical, sexual, financial or emotional) between adults who are or have been intimate partners or family members, regardless of gender or sexuality".
An adult is defined as any person aged 18 years or over. Family members are defined as mother, father, son, daughter, brother, sister and grandparents whether directly related, in-laws or step-family.
The definition is supported by an explanatory text:
"The definition acknowledges that domestic violence can go beyond actual physical violence. It can also involve emotional abuse, the destruction of a spouse's or partner's property, their isolation from friends, family or other potential sources of support, control over access to money, personal items, food, transportation, the telephone and stalking. Violence will often be witnessed by children and there is an overlap between the abuse of women and abuse (physical and sexual) of children. The wide adverse effects of living with domestic violence for children must be recognised as a child protection issue. They link to poor educational achievement, social exclusion and to juvenile crime, substance misuse, mental health problems and homelessness from running away. It is acknowledged that domestic violence and abuse can also manifest itself through the actions of immediate and extended family members through the perpetration of illegal activities, such as forced marriage, so-called 'honour crimes' and female genital mutilation. Extended family members may condone or even share in the pattern of abuse."
..........
Domestic violence is widely recognised as being a pattern of controlling and coercive behaviour, through which the perpetrator seeks to exert power over the victim. Whatever form it takes, domestic violence is rarely a one-off incident. It is often a series of incidents, including those of greater and lesser severity but often increasing in frequency and seriousness which may have a cumulative impact on the victim.
Victims of domestic violence suffer on many levels including deterioration to their health, loss of housing and disruption to education. They may lose the freedom to live their lives how they want, without fear. Pregnancy itself is may be a trigger for the beginning or acceleration of violence.