Victims of child sex abuse can appeal against decisions by the criminal justice system to shelve their cases under new measures to address high-profile failures by the authorities in child-grooming cases and the Jimmy Savile scandal.

Alleged child sex abuse in a religious institution is one of four complaints set for scrutiny by a new panel which can advise police and prosecutors to re-open their books on a case that had previously failed to reach the courts.

The move was announced by the Director of Public Prosecutions, Keir Starmer QC, as he apologised to victims who had been let down by the authorities in the past.

The unmasking of Jimmy Savile as a serial sex offender and a series of other scandals, including the failure to identify grooming gangs and the death of professional violinist Frances Andrade, who killed herself after giving evidence in court about a former abusive teacher, highlighted the need for changes to the way child sex abuse cases were handled.

The new guidance released today focuses on the needs of the victims and the importance of not dismissing their complaints, particularly if they have had troubled backgrounds, such as gang activity.

It stresses that there should be no bar to therapy for victims before their cases come to court, a complaint of the family of Ms Andrade.

It also says there is no bar to victims being told that they are not the only ones to have made complaints of abuse. Reviews of police inquiries into Jimmy Savile revealed that victims were not told about other complaints about the former BBC DJ, making them unwilling to speak out against such a powerful figure.

The director of public prosecutions, Keir Starmer, QC, said: "I accept that in the past the wrong approach was taken. When the Savile report was published I apologised then to victims in that case and I will extend it to other victims. The approach in the past was not good enough."

A new panel will sit for the first time in July to examine complaints by four people - including two about the same person - about cases that never came to court in a process that officials expect to expand rapidly in the coming years.

The five-strong panel - which will include senior police, prosecutors and the NSPCC - will examine cases where a complaint was made of childhood sex abuse but where the case was dropped and the alleged perpetrator may still pose a risk. One of the complaints has already prompted police to re-open the case before it reached the panel.