Maria Stubbings, of Chelmsford in Essex, was strangled with a dog lead in 2008 by Marc Chivers, who had already killed a previous girlfriend.
Her brother Manuel Fernandez has told ITV Daybreak that the family have been calling for a public inquiry.
He said: "This highlights issues around domestic violence with one police force but it's actually a national problem."
More top news
Tonight it'll be quite chilly leading to a cold but bright start.
Demonstrators jumped the barrier and lay down on the red carpet to draw attention to cuts to domestic abuse services.
Doctors in Australia have reattached 16-month-old Jaxon Taylor's head to his spine after he was 'internally decapitated' in a car accident.