Muriel Elliott died at Derriford Hospital in 2007
No-one is to be charged after the death in Plymouth's Derriford Hospital of a woman whose feeding tube was inserted into her lung rather than her stomach.
The Crown Prosecution Service (CPS) says there is conflicting evidence over who is responsible for what happened.
The hospital says the coroner, who will hold an inquest next year, has been handed the details of its own inquiry.
Muriel Elliott's family now wants the Health and Safety Executive (HSE) to investigate practices at the hospital.
Mrs Elliott died in Derriford Hospital in September 2007, aged 77.
She had had a nasal gastric feeding tube fitted following a stroke.
But the tube went into Mrs Elliott's lung, not her stomach, and she died of pneumonia 13 days after it was fitted.
Police conducted an 18-month inquiry at the hospital
After an 18-month inquiry, Devon and Cornwall Police handed a file to the CPS.
CPS investigator Stephen O'Doherty said: "I concluded that there was insufficient evidence to charge any individual with any offences in relation to Mrs Elliott's death.
"Because there was conflicting evidence from witnesses it would not have been possible to prove who, if anyone, approved the procedure which ultimately led to her death."
Mrs Elliott's family say that although they are happy the police did a thorough job, they would like the HSE to investigate hospital practices.
Her son-in-law Brian Gerrish said: "I think it's essential because if we don't undertake a full investigation into both the clinical side, for clinical errors, nursing errors, whatever it is, and the management of the hospital, we are not getting at the full truth of what's happened."
A spokesperson for Plymouth Hospitals NHS Trust said: "This case has been subject to a full investigation within the trust and the results and recommendations of that investigation have been shared with the coroner.
"An inquest is due to be held some time next year and therefore it is not appropriate for the trust to comment further at this time."