The Devon and Cornwall Police service has been assessed as ‘inadequate’ at investigating crime in a critical report that says not enough offenders are being brought to justice.

The region’s police and crime commissioner Alison Hernandez now says she will challenge its leaders to improve the poor outcome in such a critical function.

HM Inspectorate of Constabularies and Fire & Rescue Services (HMICFRS) says the standards of the force’s investigations “have deteriorated” because of understaffed and inexperienced teams investigating serious offences, while the service “still has work to do” in leadership and force management.

In a review of 66 cases, only 47 had an investigation plan, and it found some in which had “significant failings and victims had been let down”.

Inspectors also noted “serious concerns” about how the force manages investigations, adding that it is in “regular contact” with the acting chief constable on this issue.

Ms Hernandez welcomed the inspectors reports saying the service is good at preventing crime, and noted that data since the inspection showed improved performance in other areas, including how it manages offenders.

But she said she “shares HMICFRS’s concerns relating to crime investigation standards.”

She continued: “For several months, my recently formed accountability and standards team have been examining how files are prepared for court and how data is collected and used by the force.

“Their findings chime with those of His Majesty’s Inspector.

“The public must be confident that when they report crime the evidence and information they supply is correctly recorded and used so perpetrators are brought to book and victims receive the justice they deserve.”

She added that despite record investment in policing in Devon and Cornwall, she would be “challenging the force’s leadership to improve significantly in this area”.

In the report, Andy Cooke, HM chief inspector of constabulary, said he had “concerns about the performance of Devon and Cornwall police in keeping people safe, reducing crime, and providing victims with an effective service”.

However, the force hit back at some aspects of the report “due to the inspection being based on historical data, some of which is over a year old and does not accurately reflect improvements the force has made”.

They claimed positive feedback is evident in the force’s management of offenders and registered sex offenders, although this is still rayted as “requires improvement”.

The inspector said “considerable improvement” had been made in how the service treats people who contact it.

“Since our previous inspection, the force has made significant efforts to improve in the areas we highlighted as causes of concern or areas of improvement, which is recognised,” Mr Cooke said.

“However, despite those improvements, more is required to place the force in a position where it is consistently providing a good standard of service to its local communities.”

Acting chief constable Jim Colwell said: “I am pleased that the Inspectorate has acknowledged the good work that goes on in our neighbourhood teams every day, which is a reflection on the hard work of our officers, staff and volunteers.

“We are committed to delivering community policing with competence, compassion and common sense, which is why we remain the second safest force area in the country, and this has been clearly recognised by the Inspectorate.”

Ms Hernandez echoed this, saying the force has “one of the lowest crime rate areas.. But it is extremely disappointing that the force is letting too many victims down, whether with poor response times or a delayed investigation,” she added.

However, Mr Cooke said while aspects of crime investigation oversight had improved: “the force has understaffed and inexperienced teams investigating serious offences.

“There are delays in crime allocation and supervision, with many investigations lacking a detailed investigation plan or effective supervision.

“The force needs to improve in this area to achieve better outcomes for victims of crime.”

Decon and Cornwall Police said it has made considerable progress since the last inspection, such as review creating  more resilient teams to give more support to victims and ongoing work to address a national shortage of detectives.

“I fully acknowledge that we still have work to do to ensure that our investigations are completed to the high standards that the public would expect of us – particularly when it comes to serious and complex crimes,” acting chief constable Colwell added.

“We have made progress since the last inspection, but I recognise there is still much more to do if we are to deliver a better level of service to our communities and reduce some of the pressure on our colleagues.”

HMICFRS said it had altered its inspection process, meaning that this latest report could not be compared with the previous one.

The old system used to grade nine areas of policing, rather than eight under the new system.

Of those, two were rated inadequate (investigating crime and responding to the public), two require improvement (managing offenders, and leadership and force management), three are adequate (police powers and public treatment, protecting vulnerable people, and developing a positive workforce) and ‘preventing crime is ‘good’.

Mr Cooke praised the force for supporting neighbourhood policing teams, but raised a concern that they are “frequently being diverted to manage other demands, and this is affecting the service the force provides in this important area of policing”.

The inspector added that force now has the highest number of officers for some time.

“Although some of these officers will be less experienced, this presents a good opportunity for the force to make progress,” Mr Cooke added.

Instability at the top the force may also have been a factor in the outcomes of the report, with chief constable Will Kerr remaining suspended after more than a year.

Mr Cooke noted that operating with a temporary senior leadership team “hasn’t been easy”, and that the force is “one of the largest policing regions in England and Wales.

“The infrastructure of both Devon and Cornwall presents challenges in how the force can use resources to improve services in the areas we have identified,” he said.