Crime victims offered right of review of charging decisions
Victims of crime in England and Wales are being given the right to challenge decisions to stop prosecutions or not charge suspects.
The victims' right to review covers any decision by the Crown Prosecution Service not to pursue a case.
Director of public prosecutions Keir Starmer said victims had been treated as "bystanders" in the past.
Mr Starmer said the move could affect about 70,000 cases a year, but would not cover those dropped by the police.
Ministers and campaigners said it would improve the way the justice system dealt with victims.
BBC home affairs correspondent Danny Shaw said the CPS was confident it would not open the floodgates to tens of thousands of victims clogging up the system with appeals and delaying other prosecutions.
The new policy, which is in effect now, follows a 2011 Court of Appeal ruling which stated that "as a decision not to prosecute is in reality a final decision for a victim, there must be a right to seek review of such a decision".
The ruling referred to the case of Christopher Killick, who was jailed for three-and-a-half years for violent sexual attacks on two people who, like him, had cerebral palsy.
Killick was tried and convicted only when one of his victims complained to the CPS, prompting prosecutors to reverse their earlier decision not to press charges.
Announcing the proposals, Mr Starmer said: "The criminal justice system historically treated victims as bystanders and accordingly gave them little say in their cases."
He said this approach was supposed to inspire confidence in decisions that, once made, were final.
"But in reality it had the opposite effect," he said. "Refusing to admit mistakes can seriously undermine public trust in the criminal justice system."
Mr Starmer said the CPS currently received about 1,600 complaints per year and he expected the number of review requests to be more than that.
But he said the figure was unlikely to be "anything like" the full 70,000 cases not pursued.
The CPS currently pursues cases where its staff believe there is a "realistic chance" of a conviction, and the same test will apply when reviewing cases.
Mr Starmer said he expected the original decision to be correct in the "vast majority" of cases.
"There's no right to charge," he said. "Nobody has that, nor should they.
"If the right decision was made then it has to be upheld."
Mr Starmer said mistakes were inevitable in a justice system which deals with 800,000 defendants a year.
A CPS spokesman said reviews would be carried out by a different lawyer in the same region where the original decision was made, but if the decision not to pursue a case was upheld it would then be examined at CPS headquarters as well.
The new procedure will only apply to decisions made from now on, and can be used if there is a decision not to bring charges, to discontinue proceedings or to offer no evidence.
Baroness Helen Newlove, Victims' Commissioner for England and Wales, called the move "a positive step forward for victims and their families".
She added: "Whilst I welcome this change, I will continue to monitor the implementation of this change and challenge where necessary any shortcomings."
Charity Victim Support also welcomed the decision, saying it would strengthen victims' rights and "help to reposition victims back at the heart of our justice system".
Chief executive Javed Khan added: "Too often victims tell us that they don't have much of a voice in our justice system."
Helen Grant, Minister for Victims and the Courts, said: "If a victim has the strength to come forward, it is right that we give them every possible chance to get the justice they so deserve."
The CPS is launching a public consultation on its new policy, to see how it works in practice.
The consultation will last for three months, after which the CPS will decide whether any alterations are needed, a spokesman explained.