A baby girl died at Bristol Children's Hospital after her feeding machine was wrongly programmed and she was given a day's feed in an hour.
Maisie Bennett, who was just seven days old, was being fed intravenously after being born with a with a congenital heart defect.
She suffered a cardiac arrest and died just hours after being given 28 times the amount of formula she should have had.
Maisie had been delivered at the hospital by a planned Caesarean section on 16 August 2011. She had an atrioventricular septal defect, meaning the walls in her heart were missing.
After her arrival, she was moved to the hospital's paediatric intensive care unit for surgery, and was fed by an infusion machine which dispensed a milk substitute intravenously.
An inquest was told nurse Martyn Woods accidentally programmed the machine to deliver 210ml of feed under the hourly rate setting instead of the daily setting. He said he thought the mistake happened because when the machine beeped he assumed it indicated he needed to re-enter the 24-hour dosage.
Maisie's mum and dad, Laura Bennett and Ryan Waters from Ebbw Vale, Blaenau Gwent, said that doctors desperately tried to revive Maisie for 45 minutes, before telling them there was nothing else they could do.
"'I was numb, it was like I wasn't there and looking in on someone else's life," heartbroken Laura said.
"They asked if we wanted to be there when she passed away, but I couldn't watch her die."
The BBC reports that Laura and Ryan had previously had concerns about the care Maisie was receiving at the hospital.
"While we sat watching over our daughter a nurse was making up her feed with another," Laura said. "They were talking, laughing and joking and paid no attention to the task at hand. They seemed as though they weren't concentrating."
The hearing was also told the hospital did not follow guidelines requiring two nurses to double check rates of infusions on machines.
The inquest recorded a narrative verdict on Maisie's death.
A spokeswoman for the University Hospitals Bristol NHS Foundation Trust apologised to Maisie's family.
"Immediately following Maisie's death, the Trust conducted an indepth investigation to ensure human error like this cannot reoccur. All actions arising from these investigations have been completed or are ongoing," she said.