North Yorkshire Police has apologised after a report found the standard of its investigations into child protection matters, including child sexual exploitation, was "poor".
The force did not prioritise safeguarding matters, according to the police watchdog.
In one instance, a child at risk of sexual abuse was left unchecked for six weeks, inspectors found. The force offered "deepest apologies" to any child it had let down.
Her Majesty's Inspectorate of Constabulary and Fire and Rescue Services (HMICFRS) scrutinised North Yorkshire Police's child protection services in November.
The subsequent report found the force did not consistently provide either the quality of service or a good enough response to effectively safeguard children.
Inspectors found the way information was shared between agencies dealing with child safeguarding was "inconsistent", with cases involving missing children, child sexual exploitation or other child protection matters all being described by the force in a similar way.
The report found cases where "highly vulnerable" children who had gone missing from children's homes had been recorded as a "cause for concern", rather than "missing", so officers did not actively look for them.
In total, 73 cases where children had been at risk were examined, with practice recorded as "good" in 13 cases, "requiring improvement" in 34 cases and "inadequate" in a further 26 cases.
The report highlighted one particular instance which involved a father reporting his three-year-old daughter was at risk of sexual abuse from her mother's partner.
The force was slow to allocate the case, with delays in speaking to children's social care services and no visit to the child until six weeks after the initial call, according to HMICFRS inspectors.
"During that time, the force didn't know what risk the child was exposed to," the report said.
'Not good enough'
However, the inspection did find that staff who managed child abuse investigations were "committed and dedicated", while often working in difficult circumstances.
Andy Cooke, Her Majesty's Inspector of Constabulary, said: "The force knows it needs to do more to help its officers better understand how to safeguard children.
"We have made a series of recommendations which, if acted on, will help improve outcomes for children in North Yorkshire."
Lisa Winward, Chief Constable of North Yorkshire, said the force "fully accepted" the findings of the inspectorate.
"I offer my deepest apologies to any child we have let down or could have protected more effectively," she said.
"We haven't always got it right and we know that is not good enough for the children of North Yorkshire."
Ms Winward added: "We are working to ensure we have the right systems and processes in place to support our officers and staff to protect and safeguard every child."
