Victims of harassment and stalking are being left at risk by the police and Crown Prosecution Service with a report finding "worrying failings at every stage".
People who have suffered repeated harassment or stalking are often being let down by under-recording, inconsistent services and a lack of understanding by the criminal justice system, according to the report published by Her Majesty's Inspectorate of Constabulary (HMIC) and Her Majesty's Crown Prosecution Service Inspectorate (HMCPSI).
A joint inspection found that crimes of harassment and stalking were often missed or misunderstood by both the police and CPS.
Inspectors found cases where offenders were allowed to continue their persecution of victims, or victims were not protected with the powers in place.
The importance of the authorities' roles in identifying this type of behaviour quickly was also highlighted.
HM Chief Inspector for the Crown Prosecution Service, Kevin McGinty, said the stalking offence itself involves elements of "fixation" or "obsession" by the person who is doing it, and in some cases involves "potentially really quite dangerous people".
He added: "And people certainly have been killed as a result of such behaviour. That is why it is very important for both the police and the prosecutors to recognise this sort of behaviour at an early stage, and bring the right charges, and provide the right support to reduce that risk. Is there a risk? Of course there's a risk."
The report points out that in a recent study of 358 homicides of women in the UK, 71% were identified as involving a past or current relationship, and the study found that stalking behaviours were present in 94% of cases.
Inspectors reviewed 112 cases of stalking and harassment as part of this inspection, examining both police and CPS actions.
These were taken from six force and CPS areas across England and Wales, and while there was some evidence of good service provided by police or prosecutors, none of these 112 cases was dealt with well overall, the report said.
Her Majesty's Inspector of Constabulary, Wendy Williams, who led the inspection, said crimes of harassment and stalking are occurring more frequently now that we live in a digital world.
She added: "While we found some evidence that the police and CPS understand the risks of the repeat behaviours, as well as some examples of positive practice where victims' needs were prioritised, we found worrying failings at every stage, including reporting, investigation and prosecution.
"Changes need to be made immediately and the recommendations in the report should be acted upon without delay to protect victims from further harm."
While there are powers and protection orders in place to help prevent this kind of offending, such as Police Information Notices (PINs), inspectors found most of these were constantly misused and did not cover all types of offences.
Inspectors found that prosecutors were charging stalking offences as harassment, meaning charges did not reflect the seriousness of the offence and victims were not receiving the support they required.
Inspectors have made a series of recommendations to the Home Office, the College of Policing and the National Police Chiefs' Council, as well as forces and the CPS.
The recommendations include carrying out a review of the Protection from Harassment Act 1997, making clear the definitions of offences, conducting risk assessments for victims and the extension of prevention orders to help victims.
Alison Saunders, the Director of Public Prosecutions, said: "The CPS has made significant strides over recent years in identifying, understanding and successfully prosecuting these cases and I am pleased to note that the report highlights many instances of good practice.
"But, as this important report makes clear, there is much more that needs to be done.
"We are determined to provide a service focused on empathy towards victims and which affords them the greatest possible protection from repeat offending.
"In order to drive forward improvement in our performance we will be taking a range of steps, including the introduction of mandatory stalking and harassment training for all prosecutors. We will also work with police to update our joint protocol and ensure that we are consulting with victims' groups more effectively at a local and national level.
"It is only through this collaborative approach that we will create the criminal justice system that victims deserve."
Assistant Chief Constable Garry Shewan, the National Police Chiefs' Council lead for stalking and harassment, said: "Victims of stalking and harassment look to the police to protect them and HMIC's report shows that we must do better.
"HMIC identified areas of good practice but we now need to make sure that's happening consistently across the country.
"We will review the joint stalking protocol with the CPS and look again at how officers can use protection orders to protect people in cases of harassment as well as stalking.
"We are in the process of commissioning research to give us evidence of what works, and forces will implement new guidance from the College of Policing to help officers investigating stalking intervene early and give the right help to victims."
He added: "I will be writing to all chief constables to make sure officers are aware of the powers they have to tackle cases of stalking or harassment and that cases must be recorded and monitored in line with legislative requirements to prosecute people for the highest harm offence they have committed.
"We want to see numbers of people prosecuted for stalking and harassment increase, but we will act to safeguard victims even where a conviction isn't possible."
Karen Stephens, lead on public protection for Police Federation of England and Wales (PFEW), said: "We accept that improvements must be made. Whilst there is no easy fix or overnight solution there is much more that can be done to improve the training afforded to officers for what is a complex area of work.
"Most importantly, officers must be afforded the time to complete this training so that they can feel confident in dealing with cases and victims in the best way possible.
"As it stands they are pulled from pillar to post across many different areas of work due to existing demand."