The researchers from The London School of Hygiene and Tropical Medicine based the study on 1,000 deaths at 10 NHS trusts during 2009. The study revealed that basic errors were made in more than one in 10 cases, leading to 5.2% of deaths, which was the equivalent of nearly 12,000 preventable deaths in hospitals in England every year.

The research published in the British Medical Journal's Quality and Safety publication found that errors occurred when hospital staff made an incorrect diagnosis, prescribed the wrong drugs, failed to monitor a patient's condition or react when a patient deteriorated. Errors in omission were more frequent than active mistakes.

The majority of patients who died were elderly suffering with multiple health conditions, but the study found that some patients whose deaths were preventable were aged in their 30s and 40s.

More supervision by senior doctors is required

The study concluded that more supervision by senior doctors is required to ensure patients are appropriately assessed and communication with GP's and social services takes place.

Helen Hogan, who led the study, said: "We found medical staff were not doing the basics well enough - monitoring blood pressure and kidney function, for example. They were also not assessing patients holistically early enough in their admission so they didn't miss any underlying condition. And they were not checking side-effects... before prescribing drugs."

Hospitals must learn from careful analysis of preventable deaths and make every effort to avoid [them]."

Anne Osborn, Clinical Negligence compensation specialist at Thompsons Solicitors commented: "Any preventable death is one too many, so the NHS needs to do more to ensure every patient receives the very best care. Hopefully this study with such worrying figures will prompt the NHS to improve services and bring the death rate down"