Patient interests were neglected for years by NHS mangers as hospitals concentrated on cutting waiting times at the expense of good care, the head of the service admitted today.

Sir David Nicholson accepted that he was “part” of an environment where the leadership of the NHS “lost its focus” and which indirectly led to the unnecessary deaths of hundreds of patients at Stafford Hospital.

However he insisted that he had “no idea” about the serious care failures at the trust - where patients were routinely neglected and many died needlessly as a result of maltreatment and neglect.

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He also insisted that he had learnt his lesson and was best placed to ensure that such a scandal did not occur again.

During three hours of often hostile questioning from MPs on the Health Select Committee Sir David said that there had been assumption among senior NHS managers at the time that the care provided to patients in hospital would always be of a high quality.

But he admitted that they did not have the tools to assess if that was true and were too slow to carefully examine hospital mortality figures when they were available which could have identified problems earlier.

He also painted a vivid picture of a byzantine organisation where hospitals trusts were not sufficiently held to account by the centre for anything other than centrally imposed targets -which at times were counter-productive and led to poor care.

“During that period, across the NHS as a whole, patients were not the centre of the way the system operated,” he said.

“For a whole variety of reasons, not because people were bad but because there were a whole set of changes going on and a whole set of things we were being held accountable for from the centre, which created an environment where the leadership of the NHS lost its focus.

“I put my hands up to that and I was a part of that, but my learning from that was to make sure it doesn't happen again.”

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Addressing calls that he should resign Sir David said he believed his departure would not be in the best interests of the NHS which is under-going an unprecedented shake-up as a result of the Government’s health reforms at the same time as having to make over £20 billion of savings.

“In the next few days we will abolish over 160 organisations and we will set up another 211 local organisations and a whole myriad of national ones,” he said.

“We'll completely change the way in which we allocate resources and incentivise the NHS. At the same time, we have already lost 13,500 administrative and management staff that have all that corporate memory in them.

“So it is at maximum risk over the next few days.

“I said two years ago that I would take the responsibility of leading the NHS through this enormously complex set of changes…I am absolutely determined to do that over the next period.”

However he announced that a new contractual obligation for “candour” would be imposed so that staff would be obliged to come forward if they had concerns about care.

He also pledged that no-one working for the NHS would be asked to sign gagging orders stopping them from talking about issues that affect patients.

But during an intemperate attack on Sir David the Labour MP Valerie Vaz suggested that he was still uninterested in patients.

“What struck me about your statement (to the Mid Staffordshire Inquiry) is it is very much like you are a process man and a procedure man. I can't find anything about patients in there and what you are going to do on quality of care.”

Sir David rejected the description as “unfair”.

Speaking afterwards another committee member and former GP Sarah Sarah Wollaston said she was disappointed with Sir David Nicholson's evidence.

“He certainly didn't take responsibility for much,” she said.

“Everyone talks about David Nicholson as being the right man for the job because he's supposed to have this amazing grasp of detail, but it's more than a detail if more than a thousand people died in a hospital.”

But the Liberal Democrat MP Andrew George rejected calls for Sir David to stand down.

“I don’t think a precipitous resignation at the moment is necessarily going to help the NHS and at the end of the day I think those who concern themselves with what’s best for the NHS will want to make sure we don’t have anything that’s going to destabilise things.”

The Prime Minister’s Official Spokesman repeated Mr Cameron’s view that Sir David should not resign and was the right man to lead the NHS.