A police force has been ordered to make immediate improvements after a watchdog found it had an "inconsistent" response to child sexual exploitation.
Her Majesty's Inspectorate of Constabulary (HMIC) said its inspectors found Devon and Cornwall Police officers had a "lack of understanding" about the extent of the issue.
In some cases children were reported missing from home more than 10 times without any action taken, while in nine out of 10 of those cases inspectors found children could have been at risk of sexual exploitation.
"Officers did not always recognise that children who regularly go missing from home may be at risk of being groomed for sexual abuse," the report said.
While the force provided training to all officers and staff, not all had a "thorough awareness" of how to identify children at risk.
In one example, the case of a 13-year-old girl who sent more than 30 explicit images to an older man over the internet was closed without a suspect being identified or a referral to child social care services.
Another case involved the alleged sexual assault of a 15-year-old girl by her friend's father. While she was spoken to within two weeks, the suspect had not been arrested six months later and officers did not consider the "wider risk" he could pose.
The force responded well in the first instance to a report and in investigating it further, but recording of information was "frequently poor" and long-term strategies for safeguarding were "often absent".
HM Inspector of Constabulary Wendy Williams said: "Devon and Cornwall Police demonstrated a strong commitment to improving services for the protection of vulnerable people. However, while we found a number of examples of good work to protect children, this commitment has not yet resulted in consistently improved outcomes for children.
"We were concerned to find that in a significant number of cases we looked at, poor supervision and record keeping had undermined decision making and safeguarding measures. Some serious cases were investigated by non-specialist officers, resulting in delays, and potential risks posed by alleged offenders not being considered.
"The force must also improve how it tackles child sexual exploitation. While the force is taking some steps to address this, it still has much more to do to demonstrate that it is able to effectively identify and safeguard children at risk.
"The response to children who regularly go missing from home also requires improvement, with a particular focus on early intervention and ensuring that officers and staff understand the link between children who regularly go missing and the risk of sexual exploitation."
Devon and Cornwall Police has six weeks to respond with an action plan, HMIC said.