A Seven News investigation has revealed hospital blunders have led to dozens of serious injuries or deaths.

Secret internal documents detail the errors in Western Sydney hospitals, and outline a two year review of investigations into blunders that can mean the difference between life and death.

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61 people have died following serious mistakes over the past two years. The reasons for these deaths have until now been kept under wraps, because the information is not made public.

Those reasons include surgical material or instruments left inside patients, procedures performed on the wrong patient or wrong body part, and incorrect diagnosis.

Furthermore, a report in 2006 led to a raft of recommendations, but 40 percent of them were ignored, and 20 percent were implemented after serious delays.

Warren Anderson's 16 year old daughter died after a bungled treatment for a fractured skull.

"Vanessa should have been walking out of that hospital totally healthy," he said.

He added, "Change the system that killed my daughter to make it a safe system. That's the apology I want from Reba Meagher."

Health Minister Reba Meagher wouldn't comment, but she apologised to Mr Anderson.

Shadow Health Minister Jillian Skinner said, "I'm shocked with the extent of these deaths, given the government has denied them, is not reporting them, is failing to come clean with the extent of problems in our hospitals."

* FOI documents: [http://seven.com.au/catalogueFiles/news/media/NSWRootCauseAnalysis.pdf Read the documents uncovered in the FOI investigation]