LONDON (Reuters) - One in 10 patients admitted to National Health Service hospitals in Britain is unintentionally harmed and almost a million safety incidents, more than 2,000 of which were fatal, were recorded last year, according to a report on Thursday.

Such figures were "terrifying enough", the report by parliament's public accounts committee said, but the reality may be worse because of what it called "substantial under-reporting" of serious incidents and deaths in the NHS.

"To top it all, the NHS simply has no idea how many people die each year from patient safety incidents," Edward Leigh, the committee's chairman, said in a statement.

The committee found that some 974,000 patient safety incidents or "near misses", including 2,181 patient deaths, were recorded by the NHS but it stressed that under-reporting was a serious problem.

"(NHS) trusts estimated that on average around 22 percent of incidents and 39 percent of near misses go unreported, and that medication errors and incidents leading to serious harm are the least likely to be reported," the report said.

Leigh said the findings pointed to two "deep-seated failures": that of the NHS to secure accurate information on safety incidents and the failure "on a staggering scale" to learn from experience.

"Around 50 percent of all actual incidents might have been avoided if NHS staff had learned lessons from previous ones," Leigh said.

The report said it may take a decade or more systematically to improve safety in the NHS but that more immediate progress could be made with the introduction of electronic patient records which should reduce accidents caused by misinterpretation of doctors' handwriting.

The committee also criticized the National Patient Safety Agency, which was set up to improve safety across the National Health Service, saying there was a "question mark over the value for money" it offered.

Stephen Thornton, Chief Executive of the Health Foundation, a charity working to improve hospital safety, welcomed the committee's conclusion that more needed to be done but urged the government to provide more support.

"Hospitals need help to make sustainable, on-the-ground improvements and they need that help now," he said.