A damning report revealed a private firm which employed a German doctor who killed a pensioner on his first shift in the UK failed to act over two previous overdose incidents.
An investigation pointed to "serious failings" at every level on the handling of diamorphine – the painkiller which killed 70-year-old David Gray.
German doctor Daniel Ubani had slept for only a couple of hours the night before he gave Mr Gray 10 times the normal dose of diamorphine, and later admitted being confused about the drug.
The report found Take Care Now "failed to recognise problems" which could have prevented Mr Gray's death.
It repeatedly failed to respond to alerts over the storage of diamorphine and similar drug morphine, and had far too few staff to run a competent out-of-hours service.
Just one month before Mr Gray's death in Cambridgeshire in February 2008, a senior doctor warned in a meeting: "There is a systematic problem ... if we do not address this, it is only a matter of time before a patient is killed."
The report found Take Care Now had previously failed to act on a 2006 alert from the National Patient Safety Agency (NPSA) on the risks associated with higher doses of morphine and diamorphine.
But the firm did not make changes to the way diamorphine was used and stored until after Mr Gray's death.
Dame Jo Williams, CQC chairman, said: "Take Care Now failed on many fronts.
"Not only did it ignore explicit warnings about the use of diamorphine, it failed to address deep-rooted problems across its entire out-of-hours service. This had tragic consequences for Mr Gray.
"Since the death of Mr Gray, there is no doubt that out-of-hours care is now a high priority on the NHS agenda, and rightfully so."
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