In May and June the force took an average of almost 37 seconds to answer 999 calls – way above its own set target of 10 seconds.
It means West Midlands Police ranks bottom of all 44 forces in the country. Bedfordshire was the top performing force, taking an average of 7.1 seconds to answer 999 calls in June.
Meanwhile, one fifth of all emergency calls to West Midlands Police took longer than 60 seconds to answer in June – the poorest record of all forces.
It comes as the force battles surging demand for services, with a 40 per cent spike in 999 calls over the last six months – double the national average.
The figures were revealed in a report to the Police and Crime Commissioner's strategic board.
The report says: "WMP continue to focus upon answering all 999 calls within 10 seconds, and 101 calls within 3 minutes.
"However, with the rise in overall call demand being significant over the last 6 months (nationally there has been a 20 per cent rise in 999 demand, across WMP that rise has been 40 per cent), marginal gains have been less noticeable.
"The impact of the increased demand must not be ignored either. WMP has seen an average of 2,000+ more P1 'immediate response incidents' created per month, when compared to February-July 2021."
The report added that demand levels were putting increased strain on police resources. The force has vowed to address the failings through recruitment, the establishment of the support desk and an efficiency review.
PCC Simon Foster said the figures meant WMP was "not compliant" with its own citizens charter and service standards on either force contact or force response.
He put it down to a "chronic failure on the part of central government to invest in policing and our essential preventative public services".
"That is a big mistake, it is counter-productive and a false economy," Mr Foster added.
"It has left our over-worked and underfunded police service having to pick up the pieces. This state of affairs is expected to be exacerbated by the cost of living crisis.
"I welcome the action that is being taken by West Midlands Police to address these challenges.
"I will be subjecting this action to scrutiny, with a view to ensuring that there is an improvement in the service that the public receive."