The definition of domestic violence is to be widened to include verbal abuse and controlling behaviour, as well as teenage victims.
Campaigners welcomed the changes but warned that more funding is urgently required to help support the highly vulnerable victims.
Nick Clegg, who announced the plans, said the changes, which will be in place by March next year, "help expose the true face of domestic violence, which is much more complex and much more widespread than people often realise".
"Suffering at the hands of people who are meant to care for you is horrific at any age," he said.
"But it can be especially damaging for young people - the scars can last a lifetime.
"And to the perpetrators the message is equally simple: what you're doing is wrong and won't be tolerated."
The definition will not be written into law, but it will be broadened to include "any incident or pattern of incidents of controlling, coercive or threatening behaviour, violence or abuse between those aged 16 or over who are or have been intimate partners or family members regardless of gender or sexuality".
Deborah McIlveen, Policy and Services Manager for Women's Aid welcomed the news, saying "the challenge now is to ensure that police officers are able to identify coercive control and take appropriate action for both adult survivors and 16 - 18 year olds.
"This will require the development and implementation of procedures accompanied by comprehensive training for police officers which will require resources and leadership from the police to support this work."
The Co-ordinated Action Against Domestic Abuse (Caada) charity found 183 cases involving those aged under 18 across a two-year period, with many teenagers experiencing at least the same level of violence as adults.
Diana Barran, Caada's chief executive, said there was a "clear need" for support for young women. "It is essential that independent domestic violence advisors are funded to work with victims of all ages," she said. "The young women in our research were at high risk of serious harm or murder. Over a quarter had self-harmed and one in five were pregnant."
The Association of Chief Police Officers warned that, on average, two women a week and one man every 17 days are murdered by their current or former partner.
Chief Constable Carmel Napier, the Acpo lead on domestic abuse, said: "The amendments to the definition are key in helping to raise awareness and enable effective prevention working in partnership with all agencies.
"Domestic abuse ruins lives. In some cases it ends in homicide. This amended definition will help us all to work together to defeat this dreadful crime."
A Young People's Panel will also be set up by the children's charity the NSPCC to work with Government on domestic violence policy.
Andrew Flanagan, the charity's chief executive, said: "ChildLine receives around 3,000 contacts a year from young people about this issue.
"Teenage years are difficult at the best of times but a lack of experience in relationships and issues with self-confidence can mean young people feel they have nowhere to turn.
"Many victims, as well as perpetrators, come from abusive homes themselves and therefore don't realise how wrong these kind of relationships are."