Steve and Lynette Williams, whose 17-year-old daughter Georgia was murdered in 2013, have spoken out after a parole board declared double-murderer Colin Pitchfork fit for release.
Mr and Mrs Williams said the decision to allow Pitchfork's release "is an insult to the two young victims".
Pitchfork was jailed for life in 1988 for raping and murdering 15-year-olds Lynda Mann and Dawn Ashworth in Leicestershire.
Georgia's killer, Jamie Reynolds, was sentenced to a whole life term for her murder.
Mr and Mrs Williams are being backed in their calls by Telford MP Lucy Allan, who has written to the Lord Chancellor Robert Buckland to urge him to ensure 'life means life', and to appeal the parole board's decision over Pitchford.
In a statement Mr and Mrs Williams said the families of victims were left to deal with the consequences of appalling crimes forever, and that they should have the comfort of knowing a life sentence lasts for life.
They said: “We the parents of Georgia Williams, who was murdered at 17, by a cruel, selfish monster, wish to make a statement on behalf of victims of such crimes.
"To hear that Colin Pitchfork, who took the lives of two children for his own pleasure, is to be released, is an insult to the two young victims.
"The impact of losing a child is devastating to all parents, this is compounded when as parents, you know that the last minutes of your loved one is spent in terror.
"These monsters who commit these atrocities, destroy more than one life, they destroy whole families.
"Victims’ families are forgotten after a short while, but the terror and chaos it causes in our lives goes on and changes how we live forever. Life should mean life."
In her letter to the Lord Chancellor, Ms Allan said: "Georgia Williams was brutally murdered in Telford in 2013 by a man acting out sexual fantasies. The perpetrator received a whole life sentence. The family need to know that life means life.
"The public interest is not served by releasing such people back into our communities.
"Criminals are imprisoned to keep the streets safe as well as to serve the purpose of punishment. Whole life orders must apply to criminals in such horrific cases.
"Our constituents do not understand why the parole board has the power, and apparent inclination, to release serious convicted rapists and murderers with life sentences back into society again. I would urge you to use your power as Lord Chancellor to appeal against the parole board’s decision and ensure that Mr Pitchfork is never allowed onto the streets again.
"It is incumbent on this Government to show we are tough on crime and will protect our communities."