NHS trusts in England are routinely failing to comply with patient safety alerts issued by the National Patient Safety Agency.
Alerts are issued by the NPSA when analysis of patient safety incidents flags up potentially harmful situations in health settings, such as care after inpatient falls or improper vaccine storage.
A report from Action against Medical Accidents (AvMA) found reports that half of NHS trusts had not complied with at least one alert past the mandatory deadline and some 45 trusts had not complied with five or more alerts, some of which were years past the deadline.
The AvMA said in a statement: "Each alert not implemented leaves patients at unnecessary risk and it is inevitable that non-compliance with alerts has already resulted in patients being unnecessarily harmed or even killed."
A Department of Health spokesman commented: "Although progress has been made, much more needs to be done across the system. We expect trusts to comply with safety alerts."