An NHS watchdog has said that a significant gap" exists between the number of patients actually harmed in NHS hospitals and the figure reported by trusts adding that trusts in England and Wales need to improve their reporting of patient errors.

The Healthcare Commission said under-reporting of incidents relating to patient safety needed to be improved after data on patient safety "incidents" in individual NHS trusts showed wide variation, with some seemingly reporting no problems.

The National Patient Safety Agency (NPSA) in charge of collecting data on patient safety incidents since 2003 said the reporting of incidents is improving from just over a hundred to more than 250,000 in a three-month period.

Every year about a million reports are received from NHS trusts relating to incidents that caused patients harm or could potentially have caused harm and although a majority of these have no lasting effect on patients some cause death or disability.

The NPSA had a total of 439,612 patient's safety incidents reported between April and September 2008 in England and Wales. As per the figures out of 422 NHS organisations in England and Wales, 370 reported incidents, with the rest declining to take part or reporting fewer than 11.

In England, a total of 1,856 incidents causing death were reported while 3,643 incidents caused severe harm. 66% of the reports caused no harm to patients, 27% caused low harm, 6 % caused moderate harm while 1.4% caused severe harm or death.

In Wales, a total of 59 incidents caused death while 229 caused severe harm, 73% of incidents caused no harm, 20% caused low harm, 6% caused moderate harm and
1.3% caused severe harm or death.

Welcoming the fact that rates of reporting were increasing, Martin Fletcher, chief executive at the NPSA, said, "If we don't know where the problems are, then we can't fix them. We believe that an organisation with a high reporting rate is much more likely to have a strong commitment to patient safety and high safety standards."

Anna Walker, chief executive of the Healthcare Commission, said, "We know that a significant gap exists between the number of incidents that are reported by the NHS and the number that happen in reality.

"Trusts need to make sure they are looking carefully at this data to identify any patterns or trends and to compare themselves with other similar organisations. At the same time, trusts with low levels of reporting need to consider very carefully, whether this is accurate, and whether they truly know what is going on in their organisation."

Calling the reports on individual trusts "long overdue", Katherine Murphy, of the Patients Association, said, "Patients need local information on which to base their treatment choices.

"It needs to be in an easily understandable and accessible form or patients cannot give truly informed consent and make comparisons."