A coalition pledge urging hospitals to share violent crime data with police to help fight crime is only being carried out properly in a third of areas in England, a Department of Health (DH) report has revealed.
Sharing such information could cut violent crime by up to 40% in some areas and the failure to do so effectively has prompted public health minister Anna Soubry to write to health chiefs for an explanation.
In 2010, the Government made it clear that hospitals should share non-confidential information with police to help cut crime.
This involves telling police and local councils the time and place of assaults, the types of weapon used and the types of attack.
The data is used to paint a picture of violence in an area so resources can be better deployed to tackle it.
The DH report showed that cities and towns like Cardiff, Cambridge and Northampton have seen a drop in assaults as a result of hospitals sharing anonymised information with police.
The information-sharing programme, which has been backed by the World Health Organisation, was pioneered in Cardiff where it has been linked to a 40% reduction in violent crime after four years, the DH said.
But while almost 75% of areas in England have started to put in data-sharing systems, just a third of areas are doing this effectively, and a fifth are not doing it at all, the report said.
Only around 25% of assaults that need medical attention are reported to police, according to the DH, but when information is shared on where the crime happened and how, police can spot patterns developing and target resources effectively in hotspots.
Ms Soubry called on hospitals to improve how they share data with police, saying there are no "logistical or legal" barriers and asking them to explain any "good reasons why it cannot be done".
"We can cut the number of lives blighted by violent crime if the NHS works with the police as well as it can - which is why I have asked to see further improvements," she wrote.
"Many victims of assault go to the A&E department for treatment but do not report the incident to the police. So it's vital that hospitals work with the police by sharing anonymised information about the assault victims that they see.
"Many hospitals and police forces share information really well already and the results show this, but we want to make sure every area across the country puts this work into place."
Professor Jonathan Shepherd, director of the violence research group at Cardiff University, said:
"This approach is clearly effective and very cost effective in preventing violence, particularly violence which leads to injury.
"In Cardiff, this initiative was associated with 746 fewer violence-related A&E attendances and 87 fewer hospital admissions in 2012 compared with 2007.
"I'd encourage hospitals throughout England and Wales to adopt the same way of working and make every effort to collaborate with local safety partnerships."