A patient given a lethal overdose by an out-of-hours German doctor was "failed", a health trust said yesterday.
An investigation has been launched after Dr Daniel Ubani administered 10 times too much painkiller to David Gray, 70, while working for a health trust in Cambridgeshire last year.
The doctor, who worked for Take Care Now on behalf of the NHS, had been called to the man's home in Manea, Cambridgeshire, on February 16. Mr Gray was suffering pain caused by renal colic and kidney stones.
Chris Banks, chief executive of NHS Cambridgeshire, said: "This doctor failed Mr Gray and his family. That is something we deeply regret."
The Care Quality Commission (CQC) has pledged to investigate the case and the out-of-hours care provided by the firm Take Care Now for the NHS.
CQC head of investigations and enforcement Christine Braithwaite said: "This is a deeply disturbing case and one that must be thoroughly looked into. We have to ensure that any lessons are learned.
"We are aware of a number of concerns in relation to out-of-hours care provided by Take Care Now to the NHS. We will be looking into these issues to ensure that the interests and safety of patients are properly safeguarded."
The CQC will decide the precise scope of its inquiry in the next few days.
Dr Ubani was given a nine-month suspended prison sentence in Germany for negligence which caused Mr Gray's death.
But Mr Banks said the trust was "disappointed" that the doctor would not face a British court.
"We have supported the police in their investigation and we are disappointed that the doctor may not now be tried in the UK," he said. "Although he has been found guilty in Germany, we are concerned that Mr Gray's family may not feel that justice has been done."
He added: "We have been informed by the Strategic Health Authority that, once all investigations and avenues have been completed by the Crown Prosecution Service and the UK Police, they will be ensuring that a full investigation takes place into this case and the circumstances surrounding it. Both NHS Cambridgeshire and the out of hours provider will co-operate fully with this investigation."
According to The Guardian, Dr Ubani said he made the mistake because of confusion between drugs, one of which was not used by medics on call in Germany.
He was also under stress because he had only managed to get a few hours' sleep before his shift, the newspaper said.