Why I resigned over 'abuse failures'
Men alleged to be part of Rochdale's child grooming gang were never brought to justice because the evidence of teenage victims was not pursued, according a former police officer involved in the case.
Last May nine members of the ring were jailed for a total of 77 years.
But former detective constable Margaret Oliver told the BBC other abusers "would be off the streets" if the girl's evidence had been used.
The Crown Prosecution Service said it had focused its case on victims who would give the best evidence in court.