Officers ignored repeated warnings from the ex-girlfriend of paedophile rock star Ian Watkins that he had sent her an indecent image of a child, the police watchdog has found.
Joanne Mjadzelics took a laptop three times to Doncaster Police Station between March and May 2012, but it was only on the last time that South Yorkshire Police officers looked at it and concluded the image was a close-up of an adult.
The Independent Police Complaints Commission (IPCC) has investigated the force and found their inaction may have left a child at risk for several months.
The watchdog has concluded that three officers would have a case to answer for gross misconduct but as each has retired following 30 years' service, no further action can be taken.
One officer will face a misconduct hearing over allegations of an inappropriate remark being made to Ms Mjadzelics.
Former Lostprophets singer Watkins, 40, from Pontypridd, was jailed for 29 years in 2013 for a string of serious sex offences, including the attempted rape of a baby.
In March 2012, South Wales Police had asked colleagues in South Yorkshire to assist with allegations made by Ms Mjadzelics, who was living in the force area at the time.
Initially, the Safer Neighbourhood Team was tasked to respond, rather than specialists from the Public Protection Unit (PPU).
That led to a PC with no training in child sex abuse investigations or in handling evidence in computer-related offences conducting an initial meeting at the police station.
The IPCC said the constable did not view any image, and there was no determined effort to ascertain whether Ms Mjadzelics had evidence of child sexual abuse.
Two months later, a constable from the PPU was told to seize the laptop and to take a statement from the rocker's ex-partner, but this did not happen.
When they viewed the alleged indecent image of a child, officers believed it was a close-up of an adult.
This was on the third time she had visited the police station.
The IPCC had not been due to release its findings until later but it sent a document in error to the Yorkshire Post newspaper, which then published details about the inquiry on its website.
South Yorkshire Police Assistant Chief Constable David Hartley said that the Force entirely accepts the findings of the IPCC's investigation.
ACC Hartley said: “Our handling of this matter fell far below the standard the public or we as a service would expect, and I would like to offer my sincere apologies to Ms Mjadzelics as she received a service that was unacceptable with no support.
“As a service, we are absolutely committed to working together to protect the most vulnerable, achieve justice, and prevent future offending. We take all reports of this nature extremely seriously.
“Ms Mjadzelics had a right to expect, and demand better from South Yorkshire Police.
“The Force has made significant organisational and structural change to best serve the victims of child sexual abuse (CSA) child sexual exploitation (CSE) over the last few years.
“Five separate trials for CSA and CSE related crimes have resulted in the conviction of 24 offenders, with over 300-years imprisonment.
“Additional resources have been invested and we have set up multi-agency CSE teams across South Yorkshire, which include representatives from Social Care, the NHS and Barnado’s. All have well established links with other support agencies.
“CSA investigative teams are also now located alongside partners to ensure a multi-agency approach and that information is shared. Training has been provided to front line staff from all agencies to improve the awareness and recognition of CSA and CSE. We also work closely with survivors to improve our response and develop training for future learning.
“As a service we have made many improvements, but we fully recognise there is more to do and further lessons to be learned to develop our service to be the very best it can be.
“In March 2016, Professor John Drew published the findings of his independent review in to South Yorkshire Police’s response to child sexual exploitation.
“His report found that “considerable lessons had been learned” and that there had been “significant improvements” since the Jay Report was published in 2014.
“We wholly accept the recommendations set out by the IPCC in this report and we are actively progressing them to continue to improve and provide the highest level of this vital service to the public.”