Her Majesty's Inspectorate of Constabulary has demanded further action after inspectors found:
Officers failed to recognise children at risk of exploitation despite clear warning signs.
Lack of training had resulted in poor investigations.
250 sex offender checks were not carried out.
Year-long delays for analysis of computers and other electronic devices in a huge backlog.
Children went missing more than 10 times without any action to protect them.
And youths are unnecessarily being kept overnight in cells.
Seventeen out of 21 cases of child sex exploitation looked at by inspectors were deemed to be be 'inadequate' or 'required improvement'. The revelations led to West Midlands MEP Bill Etheridge to ask: "What they hell is going on? These crimes are the worst in society and the police need to do everything they can to root it out and we expect them to do it professionally and exceptionally. If we haven't got the right people for the job, then we need to get rid of them and get someone else in."
The inspectors' report said some improvements have been made over the past 12 months. However, it revealed there are 720 children identified as at risk of sexual abuse in the area and that police chiefs had increased the number of dedicated to its public protection unit by 370 officers plus 16 support staff.
Similar shortcomings by West Midlands Police, which is led by Chief Constable Chris Sims, in dealing with child protection were highlighted by inspectors in 2014.
Inspectors said improvements had generally been 'partially achieved' but have now made a list of new recommendations.
The report said: "The force is making some progress but inspectors were concerned that, in a number of other cases, children at risk had not been identified through the child sexual exploitation profiling process risk was not being recognised despite clear warning signs.
"Inspectors examined 21 cases involving child sexual exploitation and found 10 to be inadequate while seven required improvement. Signs of risk were missed, lines of enquiry were either not followed up or took too long, and there were failures to respond to information and intelligence and to pursue offenders.
"In most (though not all) of the cases assessed, the immediate safeguarding measures were adequate but there was often a failure to identify wider risks." It added: "The number of children identified by the force as being at risk through a quarterly child sexual exploitation assessment had increased consistently as the process evolved. Nevertheless, inspectors were concerned to find that in some other cases, officers did not display a thorough awareness of the factors associated with identifying children at risk of sexual exploitation. This resulted in poor investigations."
Inspectors have recommended that immediate steps are taken to ensure that officers and staff within specialist child protection teams receive the right training so they can investigate the full range of child abuse offences.
Within three months inspectors said they want measures in place to clear the backlog in analysing electronic devices and further work with the Crown Prosecution Service to reduce the time it takes to decide whether to charge a suspect. The force must also produce an updated action plan within six weeks. Earlier this year a police report said there was 'similarities' between the West Midlands and Rotherham where at least 1,400 youngsters have been sexually exploited by gangs.