Deficiencies in A&E care are highlighted in the report
In his latest report, Mr Michael Buckley highlights poor care by inexperienced staff in A&E and badly handled complaints as major areas of concern.
One case highlighted was that of father-of-six Ferrol Daniel, 59, who was given a mistaken diagnosis which meant life-saving treatment was delayed.
Mr Buckley said poor communication and inefficient record keeping were at the root of many of the problems he came across in his investigations.
Mr Daniel was treated at North Middlesex University Hospital in Enfield, north London, after collapsing with chest pains on 7 March, 1998.
He was seen after waiting for almost three hours, given medication and sent home.
Coughing up blood
Just a few hours later, he started coughing up blood.
He collapsed, and died from a ruptured artery.
The Ombudsman's report said his life might have been saved if he had been treated with a beta blocker to lower his blood pressure.
It also found his family's complaint was badly handled by the trust.
In a similar case, a man, known only as Mr A, was sent home by a junior doctor from Milton Keynes General NHS Trust A&E after attending with chest pains on 26 September, 1998.
He returned four days later, and was diagnosed with unstable angina, but his treatment was marred by delays.
Mr A suffered a fatal heart attack on 1 October.
The Ombudsman's report said he should have been admitted for tests on his first visit to hospital, and added prompt treatment could have saved his life.
Lost foetus
Another case highlighted by the Ombudsman involved the treatment of a woman with a history of miscarriages.
The woman, referred to as Mrs S, attended the casualty department of St Mary's NHS Trust in October 1997 when she was 13 weeks pregnant, complaining of abdominal pain.
She was not seen by a doctor for four hours, despite an initial assessment that said she should be seen within one.
The senior house officer, a junior doctor, who did examine her told her she would probably miscarry and after talking to a gynaecologist, sent her home.
She miscarried the following morning.
The ombudsman said the foetus had probably been misplaced on her return to A&E and incinerated with hospital waste, but the hospital was not honest about what had happened.
Mr Buckley said Mrs S's treatment had been "inadequate".
All three trusts have since changed their procedures.
Liaison problems
The ombudsman said there had to be sufficient support and supervision of more junior staff and adequate liaison between A&E staff and those in other specialties.
Mr Buckley told BBC News Online: "This problem is not only seen in A&E. It's something we've drawn attention to in previous reports."
The report also details 11 cases where complaints about trust's care were handled badly.
Thirteen of the cases investigated were in London, nine in the south-east, six in the north-west, four in the eastern region, and four in the Trent region.
The ombudsman detailed 47 investigations completed by his office between April and July this year.
The Department of Health said the Ombudsman's reports were an important source of information for the NHS and a valuable training resource.
She added: "We have alerted the NHS to the publication of this report, emphasising the key messages and encouraging its use both in service development and training.
"Many of the issues highlighted are being considered as part of the process of reform."
Edward Hobson, of the Consumers' Association, said: "The cases referred to the Ombudsman represent the tip of the iceberg regarding complaints about treatment on the NHS."